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Transcript of Exposure Blending
the complete guide from
camera to process
what is exposure blending?
how exposure blending works
5 when & why to auto-bracket
what is raw?
raw adjustments vs. auto-bracketing
the versatility of bracketing
10 how to auto-bracket
14 editing in photoshop
evaluating the brackets
preparing to blend
brushwork and halos
26 advanced blending
ghosting & sensor bloom
creating the selection
the overlay brush
sensor bloom & exposure blending
48 introduction to luminosity masks
creating an alpha channel
highlight vs. shadow selections
creating the luminosity mask
transitions with luminosity masks
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
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-
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.
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
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
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
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
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
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-
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-
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
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-
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
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
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.
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
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.
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.
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
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
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
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
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%
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
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.
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%
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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