1. Unit 57 – Photography Exposure

2. Correct exposure f:8 +3 stops f:2.8 -1 stop f:11 +2 stops f:4 -2 stops

3. Over exposed
F:4
Correct exposure
F:8
Under exposed
F:16
Under exposed
F:16
Correct exposure
F:8
Over exposed
F:4

4. There are three things that control exposure
ISO – film speed
Shutter speed
Aperture

5. Film speed is measured in ISO
50 ISO film is used in very bright conditions and produces very fine-grain images
125 ISO film is used in normal conditions and produces fine grain images
400 ISO film is used when the light levels are low and produces grainier images
How much more sensitive is 400 ISO film than 50 ISO film?
100 ISO film is twice as sensitive as 50 ISO
200 ISO film is twice as sensitive as 100 ISO
400 ISO film is twice as sensitive as 200 ISO
800 ISO film is twice as sensitive as 400 ISO

6. Shutter speeds are measured in seconds and fractions of a second.
The film or sensor is exposed to light for the amount of time shown.
This camera is set for This camera is set for
1/30th of a second /250th of a second

7. An exposure of 1 second lets twice as much light hit the film or sensor as an exposure of half a second
An exposure of ½ a second lets twice as much light hit the film as an exposure of ¼ second
¼ of a second is twice 1/8th of a second
1/8th is twice 1/16th of a second and so on…

8. The aperture of the lens is measured in ‘f-stops’ which are written as f:8 etc.
A one-stop change halves or doubles the amount of light getting through the lens
f:22, f:16, f:11, f:8, f:5.6, f:4, f:2.8

9. An aperture of f:11 lets in twice as much light as f:16
f:16, f:11, f:8, f:5.6, f:4, f:2.8, f2

10. Shutter speed and aperture are linked – if one goes up, the other one must go down!
Longer time
Shorter time
1/8th
f:22
1/15th
f:16
1/30th
f:11
1/60th
f:8
1/125th
f:5.6
1/250th
f:4
1/500th
f:2.8
Smaller aperture
Bigger aperture

11. An exposure meter measures how much light there is at any given time– which lets you decide the combination of aperture and shutter speed you want to use to get the effects you want.
Most cameras have one built in so you may have to do some mental maths!

12. Bracketing 3 stops over 2 stops over 1 stop over Correct exposure
under
2 stops
under
3 stops
under
1/500th
f:2.8
1/500th
f:4
1/500th
f:5.6
1/500th
f:8
1/500th
f:11
1/500th
f:16
1/500th
f:22