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  • Buxton & District U3A Digital Photography Beginners Group

    19 November 2013

    Lesson 6: Understanding Exposure

  • Buxton & District

    Digital Photography Beginners

    Programme 19 September Exploring your camera

    1 October Youve taken some pictures now what? (Viewing pictures; filing on your computer)

    15 October Printing & Composing a better picture (part 1)

    29 October Camera modes/scenes & Composing a better picture (part 2)

    5 November Simple editing to improve your pictures

    19 November Understanding exposure

    3 December Controlling exposure/focal length/perspective/composition for a better picture & Taking Pictures of people

    17 December Everything you want to know about digital photography but never dared ask.

  • Buxton & District

    Digital Photography Beginners

    Last Time

    Using Windows Photo Gallery to edit photos Fixing Red eye Straightening Cropping Adjusting exposure Retouching

    Using Picasa to edit photos A quick look at what Photoshop can do

  • Buxton & District

    Digital Photography Beginners

    Homework

    1. Try editing a few of your own pictures in Windows Live Photo Gallery or in Picasa:

    Fix red-eye

    Straighten

    Crop

    Adjust exposure

    Adjust colour

    2. Bring any questions along next time

  • Buxton & District

    Digital Photography Beginners

    This Time

    How to improve my pictures.

    Understanding Exposure

  • Buxton & District

    Digital Photography Beginners

    What is exposure?

    Exposure is measuring and controlling the amount of light from a scene which is captured in a picture.

    Under exposed Over exposed

  • Buxton & District

    Digital Photography Beginners

    What affects Exposure

    How sensitive is the

    film (or digital detector)

    Film Speed

    How much light is there

    on the subject Lighting

    How big is the hole

    letting light into the

    camera Aperture

    For how long is the

    camera collecting light

    Shutter speed 4

    2 1 1/2

    1/250 1/125 1/60

    1/30 1/16 1/8

    1/4

    1/500

    ISO

  • Buxton & District

    Digital Photography Beginners

    What affects Exposure

    How sensitive is the

    film (or digital detector)

    Film Speed

    How much light is there

    on the subject Lighting

    How big is the hole

    letting light into the

    camera Aperture

    For how long is the

    camera collecting light

    Shutter speed 4

    2 1 1/2

    1/250 1/125 1/60

    1/30 1/16 1/8

    1/4

    1/500

    ISO

  • Buxton & District

    Digital Photography Beginners

    Why should I care?

    Auto and program modes measure the lighting and automatically adjust exposure

    Sometimes you can get a different effects with different settings.

    Sometimes Auto is just wrong.

    So many cameras give you extra modes to set the exposure differently

    ISO

    ISO

  • Buxton & District

    Digital Photography Beginners

    What can you do about Lighting?

    Live

    with it

    Find additional source

    of light

    ISO

  • Buxton & District

    Digital Photography Beginners

    What affects Exposure

    How sensitive is the

    film (or digital detector)

    Film Speed

    How much light is there

    on the subject Lighting

    How big is the hole

    letting light into the

    camera Aperture

    For how long is the

    camera collecting light

    Shutter speed 4

    2 1 1/2

    1/250 1/125 1/60

    1/30 1/16 1/8

    1/4

    1/500

    ISO

  • Buxton & District

    Digital Photography Beginners

    Shutter

    The shutter blocks all light from exposing the film UNTIL you press the button.

    Then it quickly opens and closes, giving the film a brief flash of light.

    Closed Open Closed

    The longer the shutter is open the more light reaches the film.

    ISO

  • Buxton & District

    Digital Photography Beginners

    What affects Exposure

    How sensitive is the

    film (or digital detector)

    Film Speed

    How much light is there

    on the subject Lighting

    How big is the hole

    letting light into the

    camera Aperture

    For how long is the

    camera collecting light

    Shutter speed 4

    2 1 1/2

    1/250 1/125 1/60

    1/30 1/16 1/8

    1/4

    1/500

    ISO

  • Buxton & District

    Digital Photography Beginners

    Aperture Like the Iris in the eye, the aperture opens and closes to let more or less light in

    Small aperture

    Less light

    Darker image

    Large aperture

    More light

    Brighter image

    ISO

  • Buxton & District

    Digital Photography Beginners

    Aperture settings

    The size of the Aperture is measured in f-numbers, or

    f-stops.

    1 stop difference lets in twice as much light (picture is

    twice as bright)

    Examples:

    moving from f/16 to f/8 is TWO STOPS brighter.

    moving from f/5.6 to f/8 is ONE STOP darker

    moving from f/4 to f/2.8 is ONE STOP brighter

    f/2.8

    f/4

    f/5.6

    f/8

    f/11

    f/16

    f/22

    Brighter

    Darker

    ISO

  • Buxton & District

    Digital Photography Beginners

    Shutter speed settings You can control the length of time the shutter remains open by setting

    the SHUTTER SPEED

    Examples:

    sec exposure is ONE

    STOP darker than a 1 sec

    exposure.

    1/125 exposure is TWO

    STOPS brighter than a

    1/500 exposure.

    A 1/1000 exposure is

    THREE STOPS darker

    than a 1/125 exposure.

    2 sec 1 sec 1/2 sec 1/4 sec

    1/15 sec 1/30 sec 1/60 sec 1/125 sec 1/250 sec 1/500 sec 1/1000 sec 1/2000 sec

    Open for long time / slow shutter

    speed / more light / brighter

    Open for short time / fast shutter

    speed / less light / darker

    1/8 sec

    ISO

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    Digital Photography Beginners

    What is the correct exposure?

    Under exposed Over exposed 1/125 f5.6 1/60 f5.6

    ISO

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    Digital Photography Beginners

    Exercise 1- Automatic Exposure

    1. Set your camera to Auto mode. 2. Find where your camera tells you what shutter speed and aperture it is

    going to use when you are about to take a picture. 3. Take some pictures, taking particular notice of the shutter speed and

    aperture as you take each picture. 4. Take pictures in a variety of lighting conditions:

    i. Indoors and outdoors ii. Scenes with bright and dark areas iii. Sunny day & grey day (if you can find them!) iv. Sun behind you / sun in front of you.

    5. Are you happy with the exposure in all of the pictures?

    ISO

  • Buxton & District

    Digital Photography Beginners

    What if Auto gets it wrong?

    Exposure compensation function Typically adjusts exposure by 2 stops.

    Exposure compensation

    (this shot will be 1 1/3

    stops underexposed)

    ISO

  • Buxton & District

    Digital Photography Beginners

    Exercise 2 - Exposure Compensation

    1. Set your camera to program mode.

    2. Find the exposure compensation adjustment on your camera (if you have one).

    3. Try taking several pictures of the same scene at different exposures:

    i. Shoot the same scene with set to +2; +1; 0; -1; -2

    ii. Try this with several different scenes

    iii. Find some scenes which have a both bright and dark areas

    ISO

  • Buxton & District

    Digital Photography Beginners

    Shutter speed so what? 1/60 sec 1/4000 sec

    Fast (short) shutter speed freezes

    movement of the subject (or camera)

    Slow (long) shutter speed blurs

    movement of the subject (or camera)

    ISO

  • Buxton & District

    Digital Photography Beginners

    Exercise 3 Shutter Speed

    1. Set your camera to Shutter Priority

    2. Find out how to adjust the shutter speed in this mode.

    3. Change the shutter speed: i. Find the shutter speed and aperture on the camera display.

    ii. How does the camera tell you if it cant set the aperture to get a correct exposure at your chosen shutter speed?

    4. Take pictures of moving objects: i. Take some shots at fast shutter speed (1/250 or faster)

    ii. Take some shots at slow shutter speed (1/30 or slower)

    5. Find out what happens at slow shutter speeds i. Zoom in as far as your camera will allow (longest focal length or highest x zoom) and shoot outdoors at

    shutter speeds of 1/30 or less.

    ii. Zoom out as far as your camera will allow (shortest focal length or 1x zoom) and shoot a similar scene at shutter speed of 1/30 or less.

    iii. Come indoors how slow do you have to set the shutter speed to get a good exposure (without flash)?

    iv. Stay indoors what happens when you take pictures at speed of around 1/10 or 1/15.

    ISO

  • Buxton & District

    Digital Photography Beginners

    What about aperture?

    Change shutter speed Change aperture

    to keep exposure

    1/3 f22 1/13 f11 1/50 f5.6

    Motion in foreground frozen as shutter speed increases

    Foreground in focus in all shots

    Back