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Exposure Values
F-Stops, Shutter Speeds & Film Speeds

A one step change in any exposure value can be achieved by changing the f-stop, shutter speed or film (to a different roll) by one step. To maintain the same exposure value, any change in one row requires the opposite change in one of the other rows.

←Less Light                                                  More Light→
f-number
(f-stop) 		2.8 4 5.6 8 11 16 22
Shutter speed
(in fraction of seconds) 		15th 30th 60th 125th 250th 500th 1000th
Film Speed
(ISO) 		3200 1600 800 400 200 100 50

Aperture (f-stop) Priority: You choose the f-stop and the ISO. The camera calculates the shutter speed.
Shutter Priority: You choose the shutter speed and the ISO. The camera calculates the f-stop.
Program Mode: The camera chooses the best f-stop/shutter speed combination for the ISO of the film.
Note on DX Coding: Modern cameras can read the ISO of a film, thanks to the DX coding on the film cartridge. This makes aperture and shutter priority settings even easier.

Questions:
  1. Assuming you want to maintain your exposure value:

    Switching to a higher speed film means you must use a __________ aperture and/or a __________ shutter speed.

    Switching to a lower speed film means you must use a __________ aperture and/or a __________ shutter speed.
  2. Which shutter speed lets in the least amount of light?
    a) 15th
    b) 125th
  3. Which f-stop lets in the least amount of light?
    a) 2.8
    b) 22
  4. You are using ISO 100 film shooting at f/16 at 125th. A cloud passes overhead darkening the scene by one step. To maintain the exposure value, you need to change the ISO to _______, or change the f-stop to ______, or change the shutter speed to ________.
  5. Write a scenario where using Aperture Priority mode would be useful:
    Acceptable Answers describe a situation where the photographer wants to maintain depth of field.
Answers:
1. smaller, faster
    larger, slower
2. 125th
3. 22
4. 200, f/11, 60th
5. Acceptable Answers describe a situation where the photographer wants to maintain     depth of field.