Exposure Blending

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Transcript of Exposure Blending

  • the complete guide from

    camera to process

    exposure blending

    christopher odonnell

  • what is exposure blending?

    how exposure blending works

    5 when & why to auto-bracket

    auto-bracketing overview

    what is raw?

    raw adjustments vs. auto-bracketing

    the versatility of bracketing

    10 how to auto-bracket

    bracketing: step-by-step

    manual bracketing

    finaltipsonbracketing

    14 editing in photoshop

    evaluating the brackets

    preparing to blend

    theblendingworkflow

    brushwork and halos

    26 advanced blending

    whentouserefinedmasks

    ghosting & sensor bloom

    creating the selection

    refiningthemask

    the overlay brush

    sensor bloom & exposure blending

    finaladjustmentstotheblend

    48 introduction to luminosity masks

    creating an alpha channel

    highlight vs. shadow selections

    refiningluminosityselections

    creating the luminosity mask

    transitions with luminosity masks

    finishingtouches

    finalthoughts

    71 about christopher

    72 other ebooks

    73 copyright information

  • what is exposure blending?Exposure blending is one of the most powerful ways to create a stunning

    photograph. As youve probably noticed, it can be difficult to capture an entire

    landscape accurately (especially those with a sky) because your camera sensor

    is limited to one aperture and one shutter speed at a time its not possible to

    have two different settings within the same frame. Youll often note that your

    photos rarely live up to what you actually saw exposure blending is one way

    to overcome the limitations of your camera and photograph a landscape with

    the full tonal range that you see in the field.

    Simply put, in order to have a well-exposed landscape youll need one image

    exposed for the brightest tones in your photo (typically the sky) and another

    for the darkest tones (the ground, usually) when the lighting isnt suitable

    to capture it all in one exposure think of sunsets and how differently the

    natural light level is when you compare the sky to the ground. Once you have

    your two extremes, youll blend them together to make one perfectly exposed

    landscape.

    Exposure blending can also be referred to as HDR blending in the sense that

    were expanding the tonal range, and this method will create a more natural

    looking image than tone-mapping with automated software. With exposure/

    HDR blending, you have much more control over the end result by manually

    choosing exactly where you want to blend your exposures together - and

    at what strength you want the blend to be. Its a method that is entirely

    customizable to your scene, which will produce a more pleasing result.

  • In addition to these two photos on the extreme ends, a middle exposure (one thats been light metered for the

    entire image, finding a middle ground between your fastest and longest exposure) is good to have as well for

    any middle ground elements you need to blend in. At times, the gap between your fast and slow exposure may

    be so great, that you end up skipping the optimal exposure for those elements that fall in between the two. An

    example of this would be the water in the below images. Notice how the image exposed for the ground (left)

    has the water slightly overexposed, and the image meters for the sky (right) has some noticeable shadows. A

    middle exposure was needed to balance this out. For intricate images with vast tonal needs - a scene with many

    shadows and highlights - its not uncommon to have 5 or more photos of the same scene at your disposal.

    The range of your exposures will depend entirely on how bright your highlights are and how dark the shadows

    appear. For example, a cloudy day will have very little difference in exposure, but a golden hour image may have

    5 or more stops to your complete tonal range.

    The two different exposures to the left show how vast the

    differences can be in order to capture the full tonal range of the

    scene. As you can see, the setting sun caused some problems

    in exposure. The image where the foreground is exposed well

    (slower shutter speed) has an extremely overexposed sky, while

    the photo exposed for the sky (faster shutter speed) has the

    foreground in complete shadow. To get a proper exposure, I

    needed to combine these two images (in addition to my base

    exposure for the water) to get the result shown to the right. I

    dont want you to be concerned with the how part just yet

    - we will get to that later on. For now, the take-away point is

    that to get a full tonal range, youll need to combine different

    shutter speeds into one image.

    how exposure blending works

  • 1. when & why to auto-bracket

  • To get three different exposures of the same scene, you dont have to calculate your

    settings and manually input a different shutter speed. Auto-bracketing is a common

    feature with digital SLRs, which allows you to capture one photo exposed normally

    (your base image), and then will automatically expose two more one directly after

    the other - of a slower and faster shutter speed than your base. The difference in

    exposure will depend on your camera and chosen settings, but usually 2 full stops

    is the maximum increase/decrease from your base photo that you can use auto-

    bracketing for.

    This is where the term auto-bracketing comes from since youre bracketing your

    images off automatically by capturing the same scene at different exposures within

    X amount of stops.

    This allows you to capture three sequential images of different exposures without

    having to adjust your settings manually its very handy, and helps to streamline

    your workflow when youre presented with a wide tonal range that one exposure

    can not contain.

    For more intense differences in lighting - as youll often find for sunrises and

    sunsets - youll still have to adjust your settings manually to capture more of a

    range in exposure than two stops (or whatever your cameras auto-bracketing limit

    is). Ill explain how to do this soon, but first I want to show you why you should

    auto-bracket instead of adjusting just one RAW file.

    auto-bracketing overview

  • For brevity, a RAW file is the digital equivalent of a film

    negative before it is printed onto paper - the raw state

    of your image that you cant really use as a photo, but

    all the information you need to create a photo is there. A

    RAW file is just that - you cant upload a RAW file to your

    website or email it to others without special viewing

    software, but you can take that RAW file and turn it into

    a universal image.

    RAW is preferable to JPG in many ways, most notably

    because of image quality. When you take a photo in JPG

    format, it is instantly compressed - and this compression

    will take detail away from your photo, thus limiting your

    processing capabilities.

    With a film negative, you can adjust the exposure by

    exposing the negative onto your paper for longer or

    shorter amounts of time. RAW allows you to do the same

    - at least, for a limited amount of stops. Since youre

    working with the unprocessed digital negative, you

    can recover some blown highlights or blocked shadows

    by adjusting the exposure of your RAW file before

    converting it into a more universal file format for display

    or print, such as JPG or TIFF.

    You can artificially adjust the exposure of a JPG image in

    post process, but this is not a true exposure adjustment

    and will not recover any data for you. In the example

    images, we can see the true benefit of RAW when trying

    to recover these blown highlights. In Figure 1, you can

    see that while the foreground is exposed accurately, the

    sky is noticeably overexposed - a common occurrence.

    Figure 2 shows how much detail is recovered by

    reducing the exposure by two full stops in RAW editing.

    In contrast, Figure 3 displays the same reduction in

    exposure (two stops) for the JPG version. Since the JPG

    file holds no additional data, the exposure is artificially

    reduced simply by adding a layer of black tones - there

    is no recovery of data, and the photo looks noticeably

    worse than the RAW adjustment.

    RAW does have its limitations however - it does not

    give you the power to shoot blindly with no regard to

    exposure, and it is always best to achieve a proper image

    in-camera. A RAW file will typically give you two stops

    of recovery capability - if you adjust the exposure more

    than two stops beyond the original exposure, you most

    likely will not recover any additional data and will start

    to notice the quality to deteriorate.

    what is raw?

  • With RAW being such a versatile format for editing,

    why is there a need to auto-bracket when you can

    simply adjust the exposure in RAW and import all

    those exposures into one file? It would save you the

    time of setting up a tripod, taking three (or more)

    images, as well as saving on disk space I thought

    RAW was supposed to be a magical exposure

    recovery tool?

    Its always best to capture the optimal exposure for

    a scene in-camera simply because youll have more

    data in an actual photo than an image adjusted

    artificially even if its in RAW. The more data that

    is retained, the more detailed your image will be.

    Auto-bracketing is superior to RAW for the following

    reasons:

    1. You may need more range in your exposure than what RAW can offer you. Typically, you can only

    adjust your exposure +/- two full stops in RAW

    before you start to see damage depending on what

    youre photographing, you may need 3, 5 or even 10

    stops difference between your brightest and darkest

    photos.

    2. While RAW is a great, low-damage, accurate way to adjust your exposure, its still better to capture

    the image with your camera to make sure you have

    the highest quality photo.

    Im going to compare a scene where I underexposed

    my photo by two full stops using auto-bracketing

    with my camera vs. dropping the exposure in RAW.

    Taking the overexposed version that was adjusted

    in RAW from the previous page and zooming in on

    the recovered sky (Figure 1), you can see that there

    is still some overexposed areas. When compared

    to Figure 2 - the photo that I took two stops lower

    with my auto-bracketing - you can see that more

    detail was retained in the sky that RAW could not

    recover.

    So while RAW provides a great recovery tool, its

    more of a last effort way to adjust your exposure

    when you have no other alternative, or if you

    only need a very minor exposure adjustment.

    Adjusting your exposure in-camera will always give

    you a superior quality when compared to RAW

    adjustments, and is worth the extra effort of auto-

    bracketing.

    raw adjustments vs. auto-bracketing

  • the versatility of bracketingAlthough RAW can not replace auto-

    bracketing, its still a file format that

    has many benefits over JPG and should

    be used when you bracket. Not only

    is there more data in RAW format, but

    youll greatly increase your tonal range

    for editing. If you auto-bracket in JPG

    format, youll typically be taking three

    images your base image, one taken

    two stops faster, and another two stops

    slower - for a total range of four stops.

    However, if you shoot in RAW format,

    you can increase or decrease your

    exposures by two stops in post process.

    That safety net will add another two

    full stops to your range on both ends of

    your bracket, bringing your total tonal

    range up to eight stops (assuming you

    shoot three auto-bracket images in two-

    stop increments).

    Blending exposures using one RAW file

    is best for those candid shots where

    you didnt have enough time to set up a

    tripod but need to correct some blown

    highlights, or simply want to brighten/

    darken parts of your image like in

    wedding or action photography. Its

    a fantastic way to save an otherwise

    unusable photo, but if you have the

    time and ability to auto-bracket your

    landscape for exposure blending, this

    is the method which will give you the

    highest quality output with the largest

    tonal range.

    Exposure blending and bracketing is not

    just for combining bright skies with

    dark grounds you can use it in many

    different ways. You can recover blown

    highlights in water reflections, use it

    as a no-damage way to dodge and burn

    your landscapes, or to blend a brighter

    foreground with a darker sky (like

    under stormy, overcast skies).

    Another popular use of this technique

    is to blend different long exposures

    together - for example, blending an

    extended exposure that captures

    moving clouds with an image that

    shows stationary grass that would

    otherwise be windswept if taken at

    the same shutter speed as the sky: the

    possibilities are endless.

    Now that you know why we auto-bracket for exposure blending, its time to go over the in-camera workflow; the process I go through to capture those bracketed images to later blend in post process.

  • 2. how to auto-bracket

    The most important part to digital exposure blending is to auto-bracket the correct

    way, giving you a solid base to edit your image in post process. You cant create a

    stunning photo in the digital dark room you can only improve upon an already-

    proper image.

    With that in mind, Im going to show you how to execute an auto-bracket the correct

    way so that you can capture images with an outstanding tonal range, like this example.

    Ill also explain how to bracket your images manually for those instances where auto-

    bracketing is too limiting for your environment.

  • Its very important that you have a sturdy tripod

    one thats capable of withstanding the weight of your

    camera, lens, and your tripod head. Solid legs with a

    good grip are imperative to not only hold your camera

    in place, but to make sure it stays there when you

    change your settings, adjust your focus, or if a strong

    wind comes along. Even the slightest movement can

    alter your alignment, making it more difficult to

    exposure blend in post process.

    Place your camera on your tripod and adjust your

    focus properly. Please read my focusing workflow as

    this is a very important step to ensure that you have

    consistent images.

    Switch into aperture priority mode so that your

    camera will only change your shutter speed to alter

    the exposure and NOT your aperture otherwise youll

    have inconsistent depths of field, making it nearly

    impossible to exposure blend accurately.

    Follow the instructions in your camera manual to

    turn on your auto-bracketing. This is usually a simple

    process with a few clicks and adjustments.

    Press your shutter button and take three consecutive

    images. I prefer to use a remote cable release so that

    Im not actually touching my camera, which can

    lead to camera shake. Out of habit, I also lock my

    mirror which can also cause unwanted vibrations.

    When finished, review the histogram to make sure

    that you have the proper tonal range to work with

    meaning that it indicates you captured one image

    with no blown highlights and another with no blocked

    shadows.

    To the right, youll see the results of auto-bracketing

    for one particular beach scene. The top image is my

    base image one that has been metered on average

    for the entire frame (evaluative).

    The middle photo is my longest exposure horrible for

    the sky, but it eliminated the blocked shadows from

    my foreground rocks (as seen in the top image) nicely.

    Finally, my least exposed image the blown highlights

    in the first two photos have been eliminated (except,

    of course, for the center of the sun) and has given a

    nice starburst effect to the sun as well.

    bracketing: step-by-step

  • At times, you may find that your cameras auto-bracketing

    system is too limiting for the tonal range youre working with

    usually only +/- two full stops. If youre shooting a high-

    contrast scene with many highlights and dark shadows (such

    as a sunset or sunrise), four stops (two in each direction) will

    most likely not give you the full tonal range where all your

    shadows and highlights are recovered.

    When this happens, youll have to forgo the auto-bracketing

    and do it manually, which is quite simple to do.

    Auto-bracketing is a great benefit because it allows you to

    capture three exposures without having to adjust your settings.

    However, its only a time-saving feature auto-bracketing does

    nothing more than what you can do manually.

    Repeat the steps above regarding how to set up your tripod

    and your focus. Instead of turning on your auto-bracketing, just

    meter your image (in aperture priority mode) and make a note

    of your settings. The aperture you choose to use should always

    remain the same throughout your images instead, youll be

    adjusting your shutter speed for your different exposures.

    Switch into full manual mode (your instructions will tell you

    how to do this) and set your aperture and shutter speed to

    what it was when you metered. Take one image, then adjust

    your shutter speed two stops faster (underexposed) to capture

    another image.

    Check your histogram for any blown highlights if you still

    see some overexposed areas, keep increasing your shutter speed

    until they disappear. Repeat this step for your shadows as well

    continue to decrease your shutter speed (overexposed) and

    check your histogram until you see that your unrecoverable

    shadows are fully exposed.

    During this process, never change your aperture or ISO to

    ensure that you have smooth exposure blending.

    manual bracketing

  • When capturing your photos, use a remote shutter release so that youre not actually

    touching the camera. This will help minimize any blurring or camera movement.

    Additionally, take special care when youre adjusting your settings as you may

    accidentally re-adjust your tripod/camera in between photos.

    Always shoot in RAW format, preferably RAW + a low-res JPG for quick preview

    purposes. This will give you the most versatility in editing, and also an all-around

    higher quality image.

    Always set your ISO to 100. Youre using a tripod (no risk for camera shake) so theres

    no need to sacrifice image quality for a faster shutter speed, unless theres a reason

    for it (like a moving object you want to capture). The clarity and quality of your

    image may suffer if you increase your ISO too much as explained here.

    finaltipsonbracketing

  • 3. editing in photoshop

  • Now I get to see the results of my careful preparation and

    in-camera execution - blending the exposures together in

    Adobe Photoshop software to make one complete image.

    This can be achieved in any program that uses layers. For

    this guide however, I use screenshots from Photoshop.

    Once youve captured three or more RAW images of the

    same scene, open all three files in the Photoshop RAW

    editor so you can see them at once. For the example here,

    I have stacked three brackets - the top image is my middle

    (base) exposure, the next image is my overexposed bracket

    (exposed for the ground), and finally my last image is my

    underexposed bracket (exposed to retain sky detail).

    In the top screenshot, Ive clicked on my base exposure

    which shows you what is captured using evaluative

    metering - and the reason why I exposure blend. The

    foreground is in dark shadow, the sky is washed out, and its

    an overall uninteresting and dull photograph that does not

    represent the stunning scene my eyes witnessed.

    By turning on the shadow clipping indicator (bottom image),

    you can see that the areas marked in blue are underexposed-

    in other words, there is no data to work with as-is so I need

    to recover it through blending different exposures.

    evaluating the brackets

  • The same method can be used for the highlights. If I

    tick the highlight clipping indicator at the top right

    corner of my histogram, the overexposed areas are

    now shown in red.

    This is a typical result when shooting scenes with

    a high tonal range - a base image with blown

    highlights and boxed shadows that have gone

    beyond what your camera can capture in a single

    frame.

    With RAW editing, you can adjust the exposure

    slider to recover these highlights and shadows, but

    as you previously learned this is not ideal in terms

    of quality - youll have more data to work with if

    you use an image that had its exposure adjusted

    in-camera than compared to the same adjustment

    made in RAW.

    Lets say you dont have a bracket to work with,

    and just have one RAW file to adjust (like the image

    above). You would still need to go through the

    exposure blending workflow since your base image

    has both over and underexposed pixels. If I tried to

    expose this image more to recover the shadows, Id

    overexpose the sky further, and vice versa the only

    way to recover the full tonal range of this image is

    to blend different exposures together.

  • Before I go any further with my RAW adjustments, I want to ensure that Ive

    captured the full tonal range of my scene. By evaluating the outside brackets

    - my fastest and slowest exposures - I can determine if I need to perform any

    exposure adjustments in RAW to recover more detail.

    With the clipping indicators still turned on, Ill first look at my longest exposure

    (above), which is exposed to recover the shadows (blue). Except for a few rogue

    pixels - which I can easily clone out later in Photoshop - my shadows have been

    exposed enough to my liking. Im ignoring the blown out sky because that is

    not the focus of this particular bracket.

    I repeat the same process for my shortest exposure (fastest shutter speed),

    which is exposed to recover the sky detail. There are no blown highlights in

    the sky - indicated by red - so I have a solid tonal range to work with between

    these two brackets. When you compare this image to the base exposure on

    the previous page, its easy to see why exposure blending can greatly enhance

    your photography. Much interest has been recovered, and you can begin to

    visualize how your final image will look once these three exposures are blended

    together.

    I should note that these brackets are the result of a panostitch, and stitching

    rarely produces an image with perfectly straight edges. The blue chunks you

    see along the borders of the image are not part of the original scene - rather

    just black areas filling the void where the edges arent flush. Ill end up warping

    and cropping these sections out in process (shown later). My main concern

    here are the under and overexposed areas within the scene itself, and I can tell

    that Ive recovered all the data I can and am ready to proceed.

    If I did have large areas of lost data, I would adjust the affected bracket in RAW

    by sliding my exposure slider enough to bring back the details. Ideally, I would

    have done a manual bracket in the field as described earlier, but at times you

    still need to fine-tune your exposure in RAW.

  • From here, you should perform any RAW editing you

    usually do, such as black and white conversion, white

    balance adjustments, and so on. Click the Select All

    icon to have your adjustments apply to all your images

    except for any adjustments you make to your exposure.

    This helps to cut down on your editing time and keeps all

    your images uniform.

    With all three images still selected, click Open to bring

    them into Photoshop. Youll notice that your photos are

    open in three separate windows - were going to combine

    them into the same file for blending, with each image on

    its own layer.

    Select your base exposure file and click CTRL + A so that

    you see the marching ants along the edge of your

    frame. Press CTRL + C to copy the image and switch over

    to your brightest photo (longest exposure). Create a new

    layer and press CTRL + V to paste the middle exposure on

    top. If you executed your bracketing properly and used a

    tripod, you should have no alignment problems.

    Repeat this step for your underexposed image (fastest

    shutter speed) so that you have all three photos in one

    file and on their own separate layers. Your top layer

    should be your darkest image and the bottom layer

    should be the brightest.

    preparing to blend

  • theblendingworkflowFor the majority of this tutorial, Im going to be adding layer masks to create

    one image using multiple exposures its much like HDR, only with a more

    realistic appearance and completely customizable.

    First, Ill add a layer mask to blend in my sky. Click the Add Layer Mask icon

    located at the bottom of your layers palette.

    Now select your brush tool by pressing B, and ensure that your foreground

    color is set to black, and background set to white. With your new layer mask

    selected, adjust your brush to a suitable size for this image, I want to combine

    the water and ground exposure of the middle layer with the sky of my top layer.

    Make sure your brush is set to 100% opacity, and with a 0% hardness level.

    What Im basically doing here is creating an imaginary and reversible hole in

    the top layer so that I can see the middle layer. Instead of applying it directly to

    the layer, Im using a mask so that I can adjust or delete this hole later on.

    Since I only want the ground and water to poke through, I just brush over

    that particular area (i.e. I dont brush over the sky). While the base layer has

    a brighter foreground than my top layer, its not bright enough to capture a

    solid tonal range. My goal is to blend in the bottom layer for the foreground,

    but I need to cut a hole in both my top and

    middle layer in order to show the bottom

    layer - remember, layers are stacked, so

    your can not see anything beneath a non-

    transparent layer unless its masked.

    Also note that you can always switch your

    brush color to white if you want to reverse

    the brush work you previously did and

    bring back the layer you are masking.

  • In the side-by-side comparison to the left, you can see how the base exposure

    is now visible on the top layer. Im starting to see an overall improvement in

    the tonal range, and how differently the image looks when blended with a

    longer exposure.

    By pressing the ALT key and clicking on the layer mask in your layers palette,

    you can view the mask on your layer and see exactly where you brushed.

    When looking at the bottom image, you can see where the brush strokes were

    applied to create that hole, allowing the layer beneath to be visible. Since I

    used a 0% hardness, the edges of the painted areas are soft and transitional -

    depending on your image, this can be beneficial or counterproductive, so you

    should adjust your hardness to accommodate your scene.

    The brush opacity and hardness allows you to fully customize your layer mask

    to fit your content. A brush with 100% hardness will give you a very sharp

    (or hard) transition good for small areas or sharp horizons, but generally

    doesnt look realistic when youre trying to blend tones gradually. I usually

    start with 0% hardness for larger areas and readjust as necessary.

    Another great tool you can adjust is your brush opacity or transparency.

    When set at 100%, youre basically cutting a hole in your layer, allowing the

    bottom layer to be seen completely. When you reduce the opacity lets say

    to 50% youre only allowing 50% of your bottom layer to be seen and 50%

    of your top layer to remain. This allows you to blend just the right amount

    between exposures for the perfect balance of tones.

  • You can always reverse the masking you perform by inverting your

    foreground brush color. Press X to switch your foreground and background

    color - brush white to lessen your layer transparency, and black to increase it.

    My seascape is starting to improve, but the foreground is still far

    too underexposed for my liking. By selecting the base exposure, I add

    another layer mask and brush the foreground rocks and tree line with

    a 100% opacity brush set at 0% hardness (right).

    In the end, I have three exposures in one to create a well-balanced

    scene - an underexposure for the sky, the base exposure for the middle

    ground water, and the overexposure for the foreground rocks and

    shoreline. Note the changes in the histogram each time I blend a layer.

    Often youll find that using 100% opacity may cause too sharp of a

    transition on some areas and look rather unnatural. When I zoom in

    on the shoreline (bottom right), you can see that the water and rocks

    along the edge are a bit too dark and appear distracting.

    If I use a 100% opacity brush, I have to choose between either the

    base exposure (too dark) and the overexposed bracket I used for the

    foreground (too bright). Rather than choose between the two, I can

    adjust my brush opacity level to a lower percentage. This will allow me

    to blend these two layers together gradually, displaying a bit of each

    and create a more harmonious tonal range with a smoother transition

    between layers.

  • To enhance my image and make the transition smoother,

    I will mask the waters edge at a lower opacity level - in

    other words, I will paint over my mask with a black brush,

    but not at full strength.

    In Photoshop, you can highlight where you have masked

    by toggling the \ key, which will illuminate your brush

    strokes in red. The top two images show that the transition

    between layers is hard and abrupt (top right), which

    explains the unnatural look to my photo (top left).

    With a brush set at 30% opacity and set to black, I select

    my overexposure mask and begin to paint the areas I think

    are still too underexposed. If you look at the layer mask by

    pressing ALT and clicking on it in the layers palette, youll

    notice that this lower opacity brush will be varying shades

    of grey, which indicates that your brush is not at 100%

    strength.

    By brushing over the area several times with a low-opacity

    brush, I can layer my masking - gradually dissolving my

    base layer so that the longer exposure underneath starts to

    show for more accurate blending.

    When you compare the left-side images, you can see how

    natural and harmonious the layer blending appears now -

    this change of appearance is mirrored when you compare

    the two masks on the right-hand side. The bottom mask is

    now gradual and soft, slowly fading away as you approach

    the horizon line.

    Using a low-opacity brush is not only useful for working

    along edges, but for blending as a whole. If my foreground

    had been exposed too much to my liking, I could have

    masked it with a lower opacity brush - say 80% - and

    retain a small bit of darkness from my base layer. You can

    apply this method to any part of your image, and between

    any pair of layers, for a truly customized blend.

  • brushwork and halosWhen blending your layers with the brush tool, it can be a tedious job to work around

    structures and other prominent subjects that protrude between layers - such as trees

    and buildings. Try to avoid the temptation to rush through your work. After all, one of

    the top benefits of exposure blending over HDR software and using a GND filter is the

    ability to selectively blend exposures together.

    Now that I have generally blended our three exposures, its time to address the smaller

    areas - such as the rocks in the water, and the treeline in the upper left corner where

    it meets the sky. This requires a finer brush to mask these specific areas, and remove

    what we call halos - identified by the red arrows in the top image.

    Halos are the result of transitions that are too general - the brush I used was large and

    soft in order to quickly blend areas together, as seen in the mask in the bottom image.

    As a result, the blend wasnt customized to the distinct contours of my landscape,

    which produced this unnatural glow - a halo. Youll usually find halos where the

    sky exposure meets the ground exposure (as seen to the right), but they can appear

    anywhere that youve added a mask to. This requires you to return to the smaller

    details and edges of your image and work those for a flush and accurate blend.

    This is one example of where manual blending outshines HDR software and GND

    filters - you can take your brush and address halos individually and with 100% accuracy

    rather than rely on the global adjustments of software or the fixed blend from filters.

    By using layer masks, the blends are entirely reversible, and completely customizable.

  • To illustrate the importance of taking this extra

    step, Im going to blend my overexposed layer with

    my base layer to increase the exposure of this rock,

    which is isolated in the water and looks unnaturally

    dark for my landscape.

    With my brush set to 100% opacity and 0%

    hardness, I brush over the rock as carefully as I can

    - zooming in only far enough to have my subject

    fill the screen. Despite my best efforts, I have a

    noticeable halo surrounding the edges (bottom left).

    When I zoom in further to see this in greater detail

    (right) and press the \ key, you can see how my

    highlighted brush strokes spill over onto the water.

    With this closer view, I can use a smaller brush

    and remove this overflow, which will make my

    mask flush to the rocks edge. Since Im removing

    the layer mask of my overexposure, my foreground

    brush color is set to white and with 100% opacity.

    Since my brush size is small, the hardness level is

    still set at 0%.

  • When compared side-by-side, you can see how a well-

    placed mask affects the blending. The top two images

    show a mask that was applied quickly, while the bottom

    row displays more accurate brushwork that hugs the

    contours of the rocks.

    At times youll find that even the most accurate

    brushwork can make your scene appear unnatural and

    distracting as it creates a hard transition between tonal

    ranges. Youll often see this along the horizon line where

    the sky meets ground.

    After you perform your detailed brushwork, create a

    history snapshot by clicking on the camera icon on your

    history palette. This will allow you to revert back to this

    particular point in your editing in case you wish to start

    over.

    With a very low opacity brush (around 10% to start),

    begin to brush around the area where the transition takes

    place. Use 0% hardness, and experiment with different

    brush sizes to make the transition appear smooth and

    gradual - in other words, there should be no evidence of

    brush strokes or sharp transition of tones. This will allow

    you to blend these two exposures for a more gradual

    appearance, much like I did for the shoreline previously.

  • advanced blending When blending multiple exposures together in Photoshop using layer masks, youll eventually run into a situation where refining your mask with freehand

    brushwork becomes too difficult and time-consuming.

    This is especially true for intricate, jagged horizons that

    are interrupted by trees, rocks, and other elements

    such as the trees to the left. Brushing over the detailed

    contours of this tree line would require hours working

    on a pixel-by-pixel basis, which is simply unnecessary if

    you know how to refine a selection.

    The following advanced blending workflow will show

    you how to combine the longer exposure (+2 EV) of

    the trees with the faster exposure (-2 EV) for the sky,

    which eliminates all the blocked shadows and blown

    highlights and recovers any lost data from this dynamic

    tonal range. Most importantly, this step-by-step guide

    will show you how to achieve this seamless result by

    creating a refined selection that automatically masks

    these two exposures together with great accuracy.

    By exploring some of the advanced features of

    Photoshop, you can create a customized layer mask that

    instinctively hugs every contour for a truly seamless

    HDR blend of exposures.

  • whentouserefinedmasks

    Before I get into the specific workflow, I want

    to highlight when and why you should forgo

    the freehand brushwork method and rely

    on Photoshop to select your masking. If you

    would rather just skip ahead to the step-by-

    step workflow, you can jump to Creating the

    Selection. You can always come back and read

    this section if you have any why and when

    questions as you go through each step.

    A large aspect to the freehand brush method

    of blending exposures is what I call partial

    blends, where you use a low-opacity brush and

    paint over the areas you want to blend together

    gradually or rather, not 100% transparent.

    The result is a layer mask of different values,

    with a certain percentage of your top exposure

    transparent so that the exposure underneath

    can be seen to a certain degree with the goal

    being to find a happy medium between the two

    for a natural appearance and a more complete

    tonal range. You can also use the partial

    blend method in order to create a gradient-

    like appearance of tones where you gradually

    transition from one exposure to the next

    much like the effect achieved with a GND filter.

    The example images from page 22 (also shown

    to the right) show a partial blend executed well.

    Partial blends are a fast and easy way to have

    full control over how your exposures (layers)

    interact with one another by being able to

    manually adjust the opacity of the brush you

    use to blend and for most situations, this

    method works well. However, for jagged or

    serrate horizons (such as mountain ranges,

    tree lines, and other subjects that disrupt a flat

    horizon line), partial blends can present several

    side effects that detract from the success of

    your final image.

  • When I do a partial blend of my example image below in an effort to

    gradually combine the -2 EV sky and the +2 EV tree line, youll notice that

    the tree line gradually gets darker as I approach the sky. This is where the

    freehand brush method falls short, and more refined blending is necessary.

    Since the trees are interwoven into the sky line, I have to brush over these

    tree tops in order to blend in the -2 EV sky, which causes the darkened tree

    line (top). My only other option here would be to do the reverse brush

    over the tree line to blend in the +2 EV layer, which causes some unnatural

    haloing around the trees (bottom).

    When attempting to blend two exposures together with a large, low-

    opacity brush instead of using a refined mask, you generally have to

    choose between these two side-effects if your horizon line is not flat

    either darkened tree tops to compensate for the -2 EV sky, or haloing to

    compensate for the +2 EV trees. You cant blend the exposure of the trees

    with the exposure for the sky seamlessly by using a partial blend, so this

    is why pixel-by-pixel brushwork is often turned to in order to blend in

    each tree branch individually incredibly time-consuming, but the only

    way to create a truly customized blend. This is where advanced blending

    techniques come in handy because rather than resorting to either a

    partial blend (shown on the right) or tedious brushwork, you can render a

    customized, contoured selection at full opacity.

    Also, partial blends with a large brush present other issues besides this

    gradient-like effect on tones. If your layers arent uniform in alignment,

    then ghosting will appear the partial visibility of an element that is

    present in one exposure, but not the other.

  • Even the most careful in-the-field execution of your

    brackets can still produce inconsistencies between each

    exposure. A common cause for ghosting is elements that

    move within your frame such as the fluctuating tide,

    swaying tree branches, and moving clouds.

    When blending different exposures together, elements

    may have shifted, so partial blending is something you

    should avoid when alignment isnt uniform. By making

    a custom selection, you can forgo a partial blend and

    choose exactly what you want to mask, and at 100%

    opacity.

    Panoramic stitches are another example of when

    images may not be uniform in alignment, and not

    due to bracketing errors in the field. Even the most

    sophisticated panostitching software with manual

    links can produce minor discrepancies between each

    exposure, and Adobes image alignment feature doesnt

    always help either. In these instances, partial blends

    would produce ghosting and thus, more specific

    blending at 100% opacity is necessary.

    ghosting & sensor bloom

  • Sensor bloom occurs when light bleeds or overlaps onto elements in front

    of it, beyond where you would normally see the light, even with perfectly-

    aligned layers. This is especially visible in high-contrast scenes, such as the

    darkened pine trees against the sunset sky. This overexposed light spilling

    around and in between the trees in my +2 EV image has given the illusion that

    the trees are smaller, which is seen as ghosting for partial blends since the

    underexposed trees were rendered larger.

    When you compare the difference between -2 EV (exposed for the sky) and

    +2 EV (exposed for the trees), you can see how sensor bloom affects the tree

    line. The +2 EV trees were rendered considerably smaller in size due to the

    overexposed sky, and this difference will be apparent when the exposures are

    combined.

    Sensor bloom is a common occurrence with exposure blending especially

    with trees since many scenes that require blending are taken during the

    golden hours with foreground subjects backlit by the sun. Even with a

    perfectly-contoured selection with 100% opacity masking, Ill still have an

    overlap to address as the trees in the -2 EV image are larger than they are

    in +2 EV. Ill discuss how to correct this later (which is rather simple), but

    for now I want you to keep in mind what sensor blooming is and why this

    overlap would cause ghosting for partial blends.

    The only way to rectify the blending issues with partial blends is to go in with

    a very small brush and work on an almost pixel-by-pixel basis, selecting each

    individual crevice to mask out. Admittedly, Ive done this in the past (with

    great success by the way), but it took several hours of detailed work. Rather,

    theres a more automated way to select your edges by working on specific

    channels and using your overlay brush.

  • As a quick overview, Im going to create a high-contrast scene by selecting one

    channel from the layer I wish to mask. The strong contrast will serve as a way

    for Photoshop to detect a hard, contoured selection, which I can then use to

    add a customized mask.

    The typical approach for making a selection would be to use your magnetic

    lasso tool or select a specific color/tonal range. Unfortunately with these

    methods, too much guesswork is left to Photoshop which makes them highly

    ineffective for refining a selection destined for exposure blending. Often, youll

    have to re-visit the mask and contour it yourself with your brush tool, which

    defeats the purpose of automated selections.

    Once you have all your images aligned as individual layers in Photoshop (see

    Preparing to Blend), select your top layer (fastest exposure) and click the

    Channels tab to open up each individual channel for this particular layer.

    Here we can see each channel on their own layer, making it easy to identify

    which one to use for a selection. Since the goal here is to create the most

    contrast between what we want to mask and what we dont for easy edge

    detection, Im going to look for the channel that has the most contrast. For my

    image here and for most cases its the blue channel as the value disparity

    between tree and sky is higher here than the other channels.

    creating the selection

  • Since Im going to be making adjustments onto my blue channel directly in

    order to increase the contrast, I dont want that to be visible on the image

    itself. I drag my blue channel down to the create new channel icon to

    copy the channel (or just right-click and select duplicate channel). Now

    that this channel is hidden underneath the others, the changes I make here

    wont be apparent when I switch back to the Layers tab later.

  • Now Im ready to increase the contrast between sky and tree,

    which will help Photoshop detect an accurate edge for selection.

    There are several ways to go about increasing the contrast here, but

    I like using the curves tool as it gives me direct control over my

    tones. I click Image > Adjustments > Curves to bring up the curves

    tool dialog box. Notice how the channel selected is Blue copy

    the duplicate channel I just added.

    What I want to do here is eliminate that grey from the sky and

    slightly darken the tree line in other words, push the sky pixels

    closer to pure white, and the tree pixels closer to pure black. I take

    my white point and slide it over to 107 on my x-axis (input), and

    slightly increase the input of my black point to 4. This compresses

    my tonal range quite a bit, telling Photoshop to reassign most of

    those grey pixels in my sky to pure white (255).

    Whatever method you use to increase the contrast, make sure not

    to compress the tonal range to the point where the edges of your

    future selection are redefined. If you increase the contrast too

    much, you can cause the black pixels to bleed onto white, or vice

    versa. Well be refining the selection later so a perfect contrast of

    black/white isnt necessary this step is to simply create a cleaner

    canvas for easier edge detection.

    When finished, click the load channel as selection icon to create

    your selection.

  • What this will do is create a custom selection based on

    the value of each pixel which we can then apply as a layer

    mask; pixels closer to pure white (255) will have a stronger

    selection, and pixels closer to pure black (0) will be selected

    less. In other words, pure white will be 100% selected, pure

    black will not be selected at all, and the opacity of each

    selection for the varying shades of grey in between these

    two points will depend on where they fall on the value

    scale. This will make more sense visually, so Ill apply the

    selection to a layer mask so we can see the result (right).

    After the selection has been made, switch back to the

    layers palette and make sure your top layer (or whichever

    layer you want to apply your mask to) is active. Click the

    add layer mask icon to apply the selection as a mask, and

    ALT+click the actual mask to see it on your image.

    Note: I have hidden my base layer here (+/-0 EV) in order to

    access the longer exposure underneath (+2 EV) since that is

    the image I want for my tree line. Im only incorporating

    the middle ground from this base exposure (detailed here)

    so once Ive finished my masking here, Ill go back and

    activate this layer and paint in the middle ground water

    using the freehand brushwork method described earlier.

    Now we can see the result of this entire process a

    completely customized and contoured layer mask for

    incredibly accurate blending.

  • refiningthemask

    Im going to zoom out a bit so you can see the entire frame, and

    also see those shades of grey where the partial selections were

    made. When blending exposures in this manner, grey translates to a

    partial blend of exposures which is something I dont want here.

    It means that Ive only partially blended my layers, which can cause

    ghosting and an overall flattening of tones. The goal here is a pure

    white-and-black mask that is contoured to the unique horizon line.

    If I select the layer to see how this mask interacts with the blending

    of exposures, you can see how flat the tones are towards the center

    of my image, which is where the tones closest to middle grey are on

    my mask.

    While the general outline of the mask has been established, I still

    need to refine it by reassigning all those grey tones on the mask to

    either pure white or pure black. At this point, all the hard work has

    been done the borders of the mask have been outlined. Now I just

    need to fill those areas in.

  • Im going to go back and re-select my mask by

    ALT+clicking it so I can see it on my photo. What Im

    going to do here is quickly select most of the pixels I

    want to be pure black basically, everything but the

    sky and fill it with 100% black. Afterwards, Ill refine

    the edges with my brush tool.

    By selecting my lasso tool (not magnetic) and making

    sure my mask is active instead of my layer, I trace

    around the area where I want everything to be pure

    black (fully masked). Its more important to only

    select the pixels you absolutely want to mask as

    opposed to getting as close to the edge as possible.

    Well be refining the edge later (which is an easy

    process), so dont worry about leaving some breathing

    room.

    Once selected, make sure your layer mask is still

    active and click Edit > Fill. Select black as your fill

    color with 100% opacity, and click OK. Youll end up

    with a mask similar to the result below almost

    perfect, but with a slight border of various grey tones

    to refine.

  • As you can see, this is filled in quite nicely except for the top of the rock

    down in the corner. Its various shades of grey, which translates to flatter

    tones and possible ghosting in my image due to partial blending. What I want

    to do is fill in this area with pure black. In other words, everything south of

    the outline should be filled with black, and everything north should be white

    all those grey values will be pushed to either pure black or pure white.

    The easiest way to achieve this is by using the overlay brush. What this will do

    is take any pixel that is a higher value than middle grey and lighten (screen) it

    towards pure white, and inversely, it will reassign any pixel lower than middle

    grey and darken (multiply) it towards to pure black. Now you can see why it

    was important to create contrast in our channel not just to get a defined

    edge for detection, but to also push those grey pixels that were on the

    fence one way or the other, which will make the overlay brush all the more

    effective.

    I switch over to my brush tool and make sure my foreground is set to black,

    and background set to white. On the brush toolbar, change your Mode to

    Overlay from the drop-down menu and change your opacity to 50%. This

    is where I typically start with in terms of brush strength, but feel free to

    experiment with the opacity here to what suits your specific needs.

    Now its just a matter of brushing over your canvas and pushing pixels

    towards their extremes either pure white or pure black. A black overlay

    brush will push grey pixels to black, and a white overlay brush will push those

    pixels towards white. For this particular image, I paint over the sky with a

    white overlay brush to make sure that all those pixels are 100% white (not

    masked at all), and then focus in on the tree line to refine the mask selection

    (image on next page).

    I like to make several passes over the area, switching back and forth from

    black to white as I brush to keep things on an even keel. Keep in mind though

    that the more passes you make of the same color (black or white), the more

    chance it will bleed onto the other. Even pixels that are near 100% white will

    be affected by a black overlay brush if those pixels are on the border and vice

    versa and this change becomes more dramatic the stronger your opacity is.

    This can alter the size and contours of your newly-customized mask, so make

    sure to keep an eye on your brush work and take note of any changes in size.

    This is why I like to alternate back and forth from black to white as it helps to

    make sure one color doesnt dominate over the other.

    the overlay brush

  • After making several passes with an alternating black and

    white overlay brush, my mask is looking much cleaner (top

    image).

    Now I can see the refined layer mask that Ive been

    working towards completely customized to the unique

    horizon line of my image, and something that would take

    many hours to create by a freehand brush.

    Lets take a look at the results to see how this mask

    interacts with the layer exposed for the tree line (bottom

    image).

    While my mask is successful, this blend is not. Here you

    can see a common issue with this method and exposure

    blending in general inconsistent layers. However, since

    we have a custom layer mask already in place, this sensor

    bloom quite simple to fix.

  • As mentioned earlier in this tutorial, sensor bloom occurs

    when the physical area of an object is reduced in apparent

    size due to bright light sources pouring in from behind. This

    transition between light and dark is overpowering, and the

    overexposed light of the sky in my bottom layer (+2 EV) is

    bleeding over onto the trees making them appear smaller.

    The difference in size between the image exposed for the sky

    (-2 EV, where I based my mask on) and the image exposed for

    the trees (+2 EV) is quite different. Sensor bloom is why you

    see the glowing edge of light around the trees the mask

    is larger than the +2 EV trees, so its spilling over onto the

    overexposed sky of this layer.

    This can be seen when I highlight the layer mask. The trees

    of +2 EV, which has all blocked shadows in the foreground

    recovered, are masked in with a selection based on the -2 EV

    trees, which is slightly larger.

    Another issue we see here is simple inconsistencies between

    panoramic stitches those ghosting areas identified earlier.

    The software I used for panostitching rendered the -2 EV

    stitch slightly different than the +2 EV stitch, and this

    disparity affects how the mask interacts with these layers.

    This ghosting can happen for various reasons, but usually

    affects only a small area of your frame.

    sensor bloom & exposure blending

  • To rectify both the ghosting and sensor bloom, Im going to duplicate the

    ground layer underneath my mask (+2 EV) and with my clone tool, fill in to

    cover the white areas from sensor bloom. Right now, the selection I created

    for the sky layer mask (-2 EV) is too big when placed over the ground layer

    exposed for the trees. However, some select clone stamping will correct this

    unsightly distraction.

    Making sure that the duplicate ground layer is on top of the original and

    active, I select my clone stamp tool and choose a stamp source below the

    sensor bloom by ALT + clicking on the trees. I then brush over the tree line

    edges with a soft brush (0% hardness) and at 100% opacity, with a size large

    enough to cover the areas I want to correct. Both the sourcing and stamping

    are performed on the same layer, the +2 EV ground layer I just duplicated.

  • When you move about your frame, you may need to reselect new sources as you

    go along to avoid repeating any patterns for the image above, notice how I

    selected a new source area to correspond with the new stamping area. Since Im

    working with pine trees, the pattern is very chaotic and random and the mask

    is serrate, so it makes for easy stamping with no noticeable repeating patterns

    or otherwise unnatural blending. However, for other scenes, you may need to be

    more conscious on where you source your stamping and how much you perform

    before selecting a new source.

    Its also important to try and be conscious of your clone sources and where you

    stamp for example, notice how I sourced a tree trunk and stamped it where the

    tree trunk had been overwhelmed by sensor bloom as opposed to filling that area

    in with random pine needles.

  • When finished, my sensor bloom and other inconsistencies between the layers have been removed for a seamless blend.

  • Another way to relate this process to something more familiar is to think of

    filling in the edges around a stencil where the sky layer mask is the stencil,

    and the trees are what fills it. Before the clone stamping, the stencil was too

    big and only partly filled in, so the trees needed to be enlarged to occupy

    those negative spaces (the sensor bloom).

    When you take the stencil off (the layer mask) and look at the duplicate

    ground layer where I did my stamping, the appearance is rather sloppy and

    unrefined (below). However, when the stencil is put back on (previous page),

    those sloppy edges dont matter much since you only see what the mask

    (stencil) allows you to. The final result is a perfectly customized and highly

    intricate blend of exposures, where the -2 EV sky is 100% visible around every

    contour and through every gap along the horizon line.

  • finaladjustmentstotheblendWhen blending two different exposures

    together in this manner, you can sometimes

    encounter an unnatural transition where

    the foreground looks washed out against

    the background. Since the mask has already

    been drawn, and any blending discrepancies

    between each exposure corrected, I can now

    adjust the tones of +2 EV to match the sky in

    a more natural way.

    Making sure to reactivate my -2 EV layer (sky)

    that I just hid to show the stamped duplicate

    layer, I add a curves adjustment directly on

    top of the duplicate and underneath mid

    (+/-0 EV) and shift the middle tones down

    closer to pure black. The placement of the

    curves layer here is important so that it only

    affects my +2 EV image. Since Im working

    on a curves adjustment layer, I can mask out

    areas of this change where it is too drastic,

    allowing for further refinement.

  • The best approach to this would be to actually take

    an exposure at +1 EV (faster) rather than +2 EV so

    that the curve adjustment step can be skipped, but

    that can present its own unique set of issues. With

    this particular image, the darker areas to the left of

    the frame had blocked shadows at EV+1, so I instead

    chose to use +2 EV and applied the curves adjustment

    layer to reduce the tonal value closer to the horizon

    line. I then masked out any areas that became too

    underexposed such as the darker trees towards the

    left of my frame. In my eBook The Art of Processing,

    I discuss this method in further detail and explain

    how to use layer masks to selectively apply your color

    and tonal adjustments rather than settling for global

    changes.

    With this in mind, I always check my histogram in the

    field to make sure that I have recovered all lost data

    in both my highlights and shadows. In other words,

    Id rather collect too much data and adjust it in

    post as opposed to not enough and be left without a

    choice. In theory, I could have captured both an +1 and

    +2 EV frame and blended in the underexposed trees of

    +2 EV later, but that seemed like an unnecessary extra

    step since all the data is there in +2 EV.

    I have one more step to perform before I can call

    this blend complete. At times, the edges of your

    masking can be rather harsh and unnatural, making

    the transition between exposures appear pixelated. By

    refining the mask edge, you can soften this transition

    for a more pleasing appearance.

    Before I edit my mask, I want to duplicate the entire

    layer and hide it in case I need to refer back to it

    later. The Refine Mask tool can directly manipulate

    the pixels of your mask which means any changes

    to those delicate adjustments performed to create

    this mask will be permanent. By duplicating this layer

    and the mask, I have the original to revert back to if

    necessary.

    Once Ive made my duplicate, I go back to my top

    layer and right-click on the mask, which brings up

    a menu. I select Refine Mask to open up several

    powerful options most notably the Adjust Edge

    section. Since my goal is to soften the edge of my

    mask for smoother transition, I very slightly increase

    the Feather slider to .6 px, which makes quite a

    difference for this image. The amount of feathering

    you perform will depend on the size of your canvas

    since its a pixel-dependent adjustment, but a little

    goes a long way to smooth out those jagged edges.

  • Its important to note that there are several other fantastic

    options here for refining the mask most notably, the Shift

    Edge feature will allows you to increase or decrease the size

    of your mask edge. The only adjustment I need to perform to

    this mask is feathering the edge, but I want to make sure that

    you dont overlook the Refine Mask feature as it has several

    versatile tools that you should explore for future reference.

    When I compare the end result of this workflow with those

    of the freehand brush method shown earlier, you can see

    why a refined selection for my mask was preferable to simply

    painting with a low-opacity brush for a partial blend.

    While the refined mask here works much better for the unique

    challenges this horizon line presents, that is not to say that

    freehand brushwork is an inferior method to use its just

    not suited well for this particular image. For example, if this

    was a bracketed scene of a seascape with a flat horizon line,

    partial blends with a low-opacity brush would be my method

    of choice as it would create a gradient-like blending of tones

    as opposed to the harsh, abrupt transition that comes with

    a refined mask like this. In short, the method you use will

    depend entirely on the contents of your photograph one is

    not universally more effective than the other.

  • After my advanced brushwork along the sky and tree line, my layer

    blending is now complete. When you compare the final result with

    the base exposure - the image one would normally capture - you can

    see a huge difference in the tonal range and detail. This recovery of

    data is also reflected in the histograms - notice how I now have a

    nice arc distribution of tones. In contrast, the U shape of my base

    exposure indicates that I have a high amount of boxed shadows, blown

    highlights, and very little mid tones to work with. While there is no

    global definition of a good histogram, for this particular scene it has

    been improved greatly.

    The amount of blending you perform will depend entirely on your

    scene, so there is no typical workflow to follow. Your blending may

    be simpler or much more involved than this example, but thats the

    beauty of exposure blending. Its entirely customizable to compliment

    your photograph rather than trying to force your photograph to

    compliment the confines of automated software.

    When blending exposures, there are oftentimes situations where

    gradual, soft blends are preferred to make the transition between

    layers more natural for complex scenes - for example, the water middle

    ground in the top image would benefit from a softer blend as the

    transition is too abrupt. While you can soft-blend exposures together

    using a low opacity brush, like explained on page 21, theres a more

    advanced way to blend that will allow you make custom selections

    like this for scenes with complicated or dramatic tonal shifts. For the

    remainder of this eBook, Im going to introduce luminosity masks into

    the workflow, which will give you the highest level of control over

    your blends and transform the way you process your scene.

  • Luminosity masks are a powerful editing tool for

    landscape photographers as the desire to capture

    dynamic tonal ranges has become increasingly

    popular, and this often requires blending different

    exposures together in Photoshop in order to

    recover any lost detail. In the previous section on

    advanced blending, I explained how to create refined

    selections for your layer mask to assist. That method

    involves loading a custom selection based on pixels

    that were either lighter or darker than middle grey

    onto a layer mask, and then refining that selection

    to the contours of your landscape.

    An issue with this process is that it can be rather

    rudimentary for more complex images that have

    difficult transitions between exposures. To take your

    mask refinement a step further, you can select more

    specific groups of tones based on their luminosity

    level rather than whether or not they fall before or

    after 50% grey on the value scale.

    Tony Kuyper first wrote about luminosity masks in

    2006 as a way to make tone-based, local adjustments

    to one exposure in Photoshop. However, these

    masks can also be used to blend exposures together.

    Luminosity masks are simply a unique and versatile

    approach to creating a selection based on the tones

    of your image and that selection can be used to

    mask layers together in the digital darkroom.

    Luminosity masks are created by loading a selection

    that was created on a channel much like I did in

    the previous section. The difference, however, is that

    a luminosity mask does not simply create a black

    and white mask, but one based on luminance for

    gradual, natural transitions between exposures. A

    black and white mask produces a hard transition;

    when I showed you how to refine a mask previously,

    I created a strong contrast directly on the channel

    so the selection was well-defined. I then further

    refined the mask so the trees from the +2 EV layer

    were completely, 100% visible with the sky from -2

    EV. In other words, all grey tones on the mask were

    eliminated. However, this harsh transition may not

    always appear natural, and can create an unpleasant

    result when dealing with complicated, interwoven

    transitions between light and shadow for example,

    trees backlit by the sun with light rays pouring in

    from behind. For situations like this, you can create

    a soft, gradual transition between your exposures

    by selecting more specific groups of tones that are

    automatically feathered.

    introduction to luminosity masks

  • creating an alpha channel

    To begin, I want to first blend the sky of -2 EV with the foreground of +2 EV. This is basically the same thing I did in the

    last tutorial, but instead Ill go through the luminosity mask creation so you can easier understand how this works.

    Select your least exposed layer (-2 EV) and click on the Channels tab. Much like in the previous tutorial, select the

    channel that provides the most contrast overall and load it as a selection by clicking on the selection icon at the bottom

    of your palette (below) or simply CTRL/CMD + Click the thumbnail (CTRL for PCs, CMD for Macs). This will bring up the

    marching ants around pixels which are brighter than middle grey, and the strength (opacity) of that selection depends

    on how bright the pixels are.

  • Now that the selection is made, were going to save this selection

    so we can refer back to later. The easiest way to do this is to

    create an alpha channel its a duplicate of the channel youre

    basing the selection off of (in this case, the blue channel) with

    the selection applied to it. Alpha channels are simply a way

    for you to save your tonal selections to use later since you

    can always return to your Channels palette and select an alpha

    channel to activate the selection. Dont worry, alpha channels

    wont affect how your image appears since theyre hidden.

    To create your alpha channel, make sure your selection is

    still active (marching ants are still visible) and click the Save

    selection as channel icon at the bottom of your channels palette.

    This will automatically create a new alpha channel based on your

    selection. Rename this layer Highlights for easy reference as

    this is the channel youll base your future highlight selections off

    of.

  • Next, I create the Shadows alpha channel by duplicating the Highlights channel I just created and inverting it by pressing

    CTRL/CMD + I make sure that before you invert, no selections are active by pressing CTRL/CMD + D to deselect everything.

    Otherwise, inverting will only affect the selection and not the image as a whole. For easy reference, rename this alpha channel

    Shadows. Since the load channel as selection feature only selects pixels which are higher than 50% grey on the value scale

    (closer to pure white), inverting the alpha channel means that the pixels which are brighter than middle grey are actually

    your shadows.

  • What Ive done is split the two tonal ranges

    the pixels which are brighter than middle

    grey and the pixels that are darker into two

    main selection pools: Highlights and Shadows.

    These two selection groups, which are in the

    form of alpha channels, will be the source of

    all your future refined selections (at least for

    this exposure). This is what luminosity masks

    are based on making a selection on a group of

    tones either highlights or shadows in order to

    blend them with another layer. Since this method

    creates a feathered selection, the transition from

    one layer to another is almost undetectable for a

    truly natural blend with minimal posterization.

    This is where luminosity masks differ greatly from

    simply creating a black and white mask you

    can get very specific with your tonal selections

    by narrowing the parameters which define

    highlights or shadows. For example, if I only

    wanted my very brightest pixels selected in order

    to blend any blown highlights with a lesser-

    exposed layer, I would select my Highlights alpha

    channel and instruct it to only select pixels which

    are completely white (255 on the value scale). This

    is what Ill be discussing next how to take either

    of these two alpha channels and narrow your

    tonal selection to base your luminosity mask on

    later.

    Before I begin to create more refined alpha

    channels, I should note that partial blending

    should only be used when each layer (exposure)

    you are blending together is uniform in alignment

    otherwise, ghosting will be an issue. If youre

    working with only one RAW file (not ideal, but

    adequate enough if you have no other option) you

    wouldnt have to worry about any misalignment

    since youre working with the same image, so

    theres no movement between frames. If you

    bracketed off a scene and had no movement

    between frames, youll be fine as well. The

    big issue with ghosting comes when you are

    blending panoramics together even the most

    sophisticated software and seamless blend can

    still produce inconsistencies between each layer.

    So before proceeding, you should make sure that

    your layers are uniform in alignment (by first

    selecting all your layers and pressing Edit > Auto-

    Align Layers) if they are still not aligned, make

    sure you are comfortable with reversing any

    potential ghosting manually before going through

    this workflow.

    highlight vs. shadow selections

  • The overall goal here is to create a luminosity mask to

    combine the sky of EV -2 (sky) with the foreground of

    EV +2 (ground). This is what I want to focus on now, so

    Im going to deactivate my middle exposure (EV +/-0) and

    hide the layer so that there is nothing between the sky

    and ground layers (top right). Ill be bringing this layer

    back in the next step in order to gradually blend in the

    water since the middle layer has the best exposure for it.

    Since the layer we are selecting is quite underexposed

    (sky), there arent going to be any highlights for our

    selection. This is confirmed when we look at the levels

    histogram for this particular exposure (bottom right).

    Almost all of the tones are to the left, which means the

    Highlights alpha channel which only allows pixels

    brighter than middle grey to be selected is useless.

    Instead, what Ill do is base my selection on the Shadows

    alpha channel which has a vast selection pool to choose

    from and then invert my mask. If youre lost already,

    dont worry visuals help, so Ill walk you through this

    tutorial step-by-step.

    refiningluminosityselections

  • To begin, Ill select the Shadows alpha channel by clicking

    on the thumbnail, and then activate the selection by CTRL/

    CMD + clicking the thumbnail again.

    By looking at the selection here, you can see that while

    all of the shadows are selected, theres still quite a bit of

    sky detail that I dont want. This is where the true power

    of the luminosity mask comes in, the ability to condense

    and refine a selection based on the value of each pixel. In

    other words, my selection is too general right now and has

    overlapped into the sky. With a luminosity mask, I can tell

    Photoshop to take this selection pool and narrow it down

    to only include the darker shadows of this channel.

    You can compare this process to wood carving or clay

    sculpting I have the general outline of my figure, but

    need to whittle away some of the rougher selections in

    order to refine and mold it into what I want. Its been a

    long explanation so far, but quite worth it when you see

    the power of this process and why many photographers

    use luminosity masks for their photography beyond

    exposure blending.

  • What Im going to do here is take this alpha channel and intersect the selection with itself, which will tell Photoshop

    to eliminate those pixels on the very edge of the selection the lighter shadows and only select darker tones: in

    other words, reshape and refine. To do this, press CTRL/CMD + ALT + SHIFT all at once, and click on the thumbnail for

    the Shadows alpha channel.

    Here you can see the difference only one intersection made see how the selection now hugs the contours of the tree

    line, and the sky is (almost) completely deselected?

  • The next step would be to save this selection to use

    later by pressing the save selection as channel icon and

    renaming the channel for easier future reference. I like to

    simply add a roman numeral when I intersect channels, but

    feel free to use your own labeling methods.

    Looking at the refinement of this selection, youll notice

    how similar it appears to the one I created in the previous

    section on advanced blending, where I added contrast to

    the channel directly in order to refine my mask. However,

    theres one very important difference with luminosity

    masks which isnt apparent by simply looking at the

    selection here the selection is self-feathering, which

    means that the transition from one exposure to another

    will be very soft and gradual. The marching ants you see are

    simply pixels that are selected with more than 50% opacity,

    but pixels which are selected with less than 50% opacity

    will not be outlined by the marching ants. So its possible to

    have no marching ants on your alpha channel and still have

    a selection.

  • I need to refine this selection a bit more in order to get the results I want, which is everything but the

    sky. I intersect the selection once again, making sure

    that my Shadows II alpha channel is active and the

    selection is loaded. CTRL/CMD + ALT + SHIFT while

    clicking on the layer thumbnail will again further

    refine it to select even darker shadows.

    Im going to stop intersecting here since the next

    intersection starts to cut into the tree line a bit

    too much. You can do this process as many times

    as you need to, and can actually create your own

    set of Photoshop actions to do this process for you

    automatically.

    You can do the same exact process for your

    Highlights, gradually narrowing your selections

    until only your very brightest areas are chosen a

    good selection method for working on any blown

    highlights. For this particular exposure, the scene is

    quite underexposed so it made more sense to base

    my selections off of the Shadows alpha channel.

    However, if I was working with EV +2 or any other

    overexposed layer, I would have created luminosity

    masks based on the Highlights alpha channel and

    selected the overexposed sky for my masking. So

    the channel you choose to work with for blending

    either Highlights or Shadows will depend on the

    exposure of the image you are basing it off of, and

    also your intent (what areas you want to select for

    masking later).

    My channel work is done; the selections have been created for blending. However, this is only half the process I need to transfer these selections over to my layer and apply them as a mask to blend the exposures

    together. This process is rather simple, and there are several ways to apply your selection and create the mask.

  • Now that the selections have been made and saved as alpha channels, its time to turn them into a luminosity mask and

    blend the exposures together for an HDR photo. Turning a selection into a mask is quite simple, and Ill go over two

    different ways to approach this.

    First make sure that your selection is active, and is based on the correct alpha channel for this image, its the Shadows III

    channel. You can activate this by first clicking on the channel thumbnail to highlight it, and then CTRL/CMD + Click on the

    thumbnail again to bring up the marching ants. Once the correct selection is active, switch back to your layers palette and

    select the layer you wish to apply the mask to. Apply a new mask to your layer, and the selection will transfer over.

    creating the luminosity mask

  • Alpha channels are based on selections of pixels that have higher concentrations

    of white the closer a pixels value is to 100% white, the higher the opacity is

    for that selection. When you apply an alpha channel selection to your mask,

    youre transferring over the tonal ranges of that channel directly to the mask. In

    other words, your channel looks exactly like what your mask is going to be. For

    this particular image, since the mask was inverted for shadows, its doing the

    exact opposite of what I want it to do the sky is predominantly black and the

    foreground white, which means that the sky is actually getting masked out and

    the foreground is still visible. This is a simple though as all I have to do is invert

    my mask by pressing CTRL/CMD + I and since Im aware of this beforehand, Ill

    hold down the ALT key when I apply the layer mask to instantly invert it.

  • This blend is starting to come together, but for this particular set of exposures

    a gradual transition does not work well especially for the tree line. Theres

    also some sensor bloom and ghosting issues to address. Referring back to the

    previous advanced blending workflow, I refine my mask to eliminate all the

    grey tones by filling the foreground with black and sky line with white first

    generally with the lasso tool, and then more specifically with the overlay brush.

  • After refining the edge of my selection, the result is a fully

    contoured mask.

    As far as masking goes, this is exactly what I want the +2

    EV tree line and foreground blended seamlessly with the -2

    EV sky. However, this hard transition does not look natural

    for my middle ground and horizon line. The water you see in

    the bottom right image is from the +2 EV layer, which is quite

    overexposed when compared to the -2 EV sky, so this dramatic

    jump of 4 stops is too harsh.

    Another option would be to blend in the water from -2 EV, but

    this appears to be just as unnatural (inset). A gradual blend

    is needed to transition softly from the -2 EV sky to the +2 EV

    foreground by introducing a third exposure the base image

    (+/-0 EV) which I hid at the beginning of this eBook.

  • transitions with luminosity masks

    To begin, Ill unhide my base exposure and switch to the Channels palette. Here

    youll notice something new all the alpha channels I created based on -2 EV are

    still accessible. This is very useful since the alpha channel selections you create

    can be applied as a luminosity mask to any layer (exposure).

    For this image, however, I want to create a new alpha channel based on my

    middle exposure as that has the greatest contrast between the water and the

    surrounding land my goal here is to create a selection around the water and

    isolate it, and then gradually blend in the water exposure of +/-0 EV with the +2

    EV exposure to softly transition between these two extreme tonal groups.

  • Looking through my RGB channels, blue provides the greatest amount of contrast so I create an alpha channel just like I

    did before load the selection, and then save that selection as a channel (Highlights I mid below).

    Since my goal is to just select the water for blending, I intersect this selection once to further target the brighter

    highlights: CTRL/CMD + ALT + SHIFT and click on the alpha channel thumbnail, and then save the selection as another

    channel (Highlights II mid).

  • At this point I would normally just add a

    layer mask and refine as necessary, like I did

    previously. However, for gradual transitions,

    you may want to apply your luminosity mask

    in a different manner than simply loading

    it directly onto a layer mask. I find it more

    successful to transfer over just the selection

    made with your alpha channel, and create your

    luminosity mask by manually blending it in

    with the brush tool at a low opacity level. Its

    a lot like what I did earlier in the eBook on

    manual blending, but now I have the confines

    of a feathered selection that I can simply fill

    in in other words, the selection I created acts

    as a mold that I can then paint my luminosity

    mask into, and at varying transparency levels.

    To do this, make sure your alpha channel

    selection is not active (no marching ants) by

    pressing CTRL/CMD + D to deselect. Then switch

    over to your layers palette, select the correct

    layer and add a mask. The color of your mask

    is an important consideration here depending

    on what you want to accomplish remember,

    white retains and black removes your layer.

    Since my alpha channel selection is based on

    what I want to keep the water the mask

    will have to be black as I can only paint within

    the confines of that selection. To add a black

    mask, I hold down the ALT key while pressing

    the add layer mask icon.

  • Now that the mask has been applied, switch back over to your

    Channels palette and load the selection you just created. Once

    the selection is active again, simply return to your layers palette,

    select your mask, and begin to paint your luminance selection

    onto the mask with a white brush.

    I recommend you begin by using a very low opacity brush to

    gradually apply your luminosity mask sele