Buxton & District U3A Digital Photography Beginners Group Lesson 6: Understanding Exposure. 19 November 2013

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1 U3A Group Lesson 6: Understanding Exposure 19 November 2013

2 Programme Buxton & District 19 September Exploring your camera 1 October You ve 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.

3 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

4 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

5 This Time How to improve my pictures. Understanding Exposure

6 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

7 What affects Exposure How much light is there on the subject Lighting How big is the hole letting light into the camera Aperture 1/4 1/ /8 1/16 1/30 1/60 1/125 1/250 1/500 For how long is the camera collecting light Shutter speed How sensitive is the film (or digital detector) Film Speed

8 What affects Exposure How much light is there on the subject Lighting How big is the hole letting light into the camera Aperture 1/4 1/ /8 1/16 1/30 1/60 1/125 1/250 1/500 For how long is the camera collecting light Shutter speed How sensitive is the film (or digital detector) Film Speed

9 Why should I care? Buxton & District 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

10 What can you do about Lighting? Find additional source of light Live with it

11 What affects Exposure How much light is there on the subject Lighting How big is the hole letting light into the camera Aperture 1/4 1/ /8 1/16 1/30 1/60 1/125 1/250 1/500 For how long is the camera collecting light Shutter speed How sensitive is the film (or digital detector) Film Speed

12 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.

13 What affects Exposure How much light is there on the subject Lighting How big is the hole letting light into the camera Aperture 1/4 1/ /8 1/16 1/30 1/60 1/125 1/250 1/500 For how long is the camera collecting light Shutter speed How sensitive is the film (or digital detector) Film Speed

14 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

15 Brighter Aperture settings f/2.8 The size of the Aperture is measured in f-numbers, or f-stops. Darker f/4 f/5.6 f/8 f/11 f/16 f/22 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

16 Shutter speed settings You can control the length of time the shutter remains open by setting the SHUTTER SPEED Open for long time / slow shutter speed / more light / brighter Open for short time / fast shutter speed / less light / darker 2 sec 1 sec 1/2 sec 1/4 sec 1/8 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 Examples: ½ 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.

17 What is the correct exposure? Under exposed 1/125 f5.6 1/60 f5.6 Over exposed

18 Exercise 1- Automatic Exposure Buxton & District 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?

19 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)

20 Exercise 2 - Exposure Compensation Buxton & District 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

21 Shutter speed so what? 1/60 sec 1/4000 sec Slow (long) shutter speed blurs movement of the subject (or camera) Fast (short) shutter speed freezes movement of the subject (or camera)

22 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: Buxton & District i. Find the shutter speed and aperture on the camera display. ii. How does the camera tell you if it can t 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.

23 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 Background focus more blurred as aperture increases

24 1. Set your camera to Aperture Priority Exercise 4 Aperture 2. Find out how to adjust the aperture in this mode. 3. Change the aperture: i. Find the shutter speed and aperture on the camera display. ii. Buxton & District How does the camera tell you if it can t set the shutter speed to get a correct exposure at your chosen aperture? 4. Take pictures of scenes with object(s) in the foreground which are clearly separated from the background: i. Take shot at a wide aperture (f/4 or larger) ii. Take shot at small aperture (f/8 or smaller) 5. Take pictures in a range of lighting conditions. 6. Can you always find a viable shutter speed for the aperture you have chosen?

25 Exercise 5 Manual Exposure 1. Set your camera to Manual Exposure (if you have one) 2. Find out how to adjust the aperture and shutter speed in this mode. 3. Find out how your camera tells you if the shutter speed / aperture combination gives a correct exposure. 4. Try taking a range of shots i. take pictures in various lighting conditions ii. iii. iv. freeze motion show motion by blurring the image isolate an object from the background (object in focus, background blurred) v. foreground and background both in focus 5. Do you have more of a range of shutter speed or aperture?

26 What affects Exposure How much light is there on the subject Lighting How big is the hole letting light into the camera Aperture 1/4 1/ /8 1/16 1/30 1/60 1/125 1/250 1/500 For how long is the camera collecting light Shutter speed How sensitive is the film (or digital detector) Film Speed

27 What about? How sensitive is the film (or digital detector). Sometimes you have to use a very slow shutter speed even at maximum aperture (shaky picture). If you had a more sensitive film you could speed up the shutter & stop the shake. With a digital camera you can just change the setting. Digital cameras usually have automatic setting. Digital cameras usually also allow manual selection.

28 Settings How sensitive is the film (or digital detector) Is 2x more sensitive than -100 Needs ½ as much light Needs 1 stop less light -400 Is 4x more sensitive than -100 Needs ¼ as much light Needs 2 stop less light -800 Is 8x more sensitive than -100 Needs 1/8 as much light Needs 3 stop less light Is 16x more sensitive than -100 Needs 1/16 as much light Needs 4 stop less light

29 Exercise 6 1. Find out how to adjust the on your camera. 2. Set to Auto. 3. Take pictures in a range of lighting conditions note the, shutter speed and aperture. 4. Choose the shutter speed (shake/freeze/blur) and aperture (depth of field) then see if you can adjust the to get a correct exposure. 5. Take a picture with the lowest you have and a similar picture with the highest. Can you see any difference in quality of the image?

30 Common Camera Modes Aperture Priority You set the f-stop and the camera tries to set shutter speed to get a good exposure. Buxton & District Shutter Priority You set the shutter speed, and the camera tries to set the aperture to get a good exposure. Manual Full manual control, you must set both the shutter speed and the aperture. Landscape camera will attempt to capture detail in foreground and background by using high f-stop. Portrait To attempt to blur out the background, camera will try to use the smallest available f-stop. Sports To freeze motion, camera will use the highest shutter speed possible. Usually available on SLRs Not available on all compacts Camera sets shutter speed and aperture to get programmed effect.

31 Summary (what have you got to tinker with) Buxton & District Exposure Depth of field Brighter/Darker Motion / Still

32 Homework Buxton & District Go through Exercises 1-6 again at home in your own time. Make sure you feel comfortable with: Controlling exposure Freezing / blurring motion Controlling depth of field

33 Next Time How to improve my pictures. Drawing together exposure / focal length / perspective Taking pictures of people

34 Course notes I will put this presentation on the Buxton and District U3A website at : Or 1. Go to 2. Select Groups 3. Select : 4. Select materials from previous sessions from the links on right hand side of page

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