COMM 242, Advanced News Photography (Photojournalism)

Exercise: exposure combinations

Keep in mind that f/stops, shutter speeds and film/digital sensor speeds are nearly always related by precisely half or double. That is, changing your f/stop from, say, 4 to 5.6 (one stop) is the same as changing your shutter speed from 125 to 250. Each lets in half as much light. ISO numbers too are measured in comparably: 100 is half as sensitive to light as 200; 400 is twice as sensitive as 200, etc. So if you want to change f/stops, shutter speeds or ISO numbers while maintaining the same exposure, you need to also adjust the other variables.

Standard f/stops: 1.4 (widest opening), 1.8 (or 2), 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45. Most cameras can set half stops.

Standard shutter speeds: 1 (one second, slow shutter speed), 2 (half second), 4, (1/4 second, etc.) 8, 15, 30, 60, 125, 250, 500, 1000, 2000. Many digital cameras can set half shutter speeds.

Standard ISO speeds: 100, 200, 400, 800, 1600, 3200.

Try using these for the exercises below.

Your camera is set to manual mode. Your light meter shows you a combination of f/stop and shutter speed as indicated. Assuming you wish to maintain the same amount of light striking the film for proper exposure, calculate the comparable numbers for each alternative.

Example:

Your indicated f/stop is 11. Shutter speed is 125. You want a more shallow depth of field, so change your f/stop to 5.6. That lets in two stops more light. To compensate, your shutter speed will be____? Answer: 500. (Two stops less light, to compensate for two stops more light based on change in f/stop.)

But you also want a still faster shutter speed than 500. To achieve this, you must change your ISO number. It's currently set at 400. To obtain a shutter speed of 1000, you must set your ISO number at____? Answer: 800, equivalent of one stop more light (more sensitive).

1. Indicated f/stop: 5.6. Indicated shutter speed: 125.
You wish to change your f/stop to 4. Your shutter speed will be____?

2, Indicated f/stop: 5.6. Indicated shutter speed: 125.
You wish to change your f/stop to 8. Your shutter speed will be____?

3. Indicated f/stop: 5.6. Indicated shutter speed: 125.
You wish to change your f/stop to 11. Your shutter speed will be____?

4. Indicated f/stop: 16. Indicated shutter speed: 60.
You wish to change your f/stop to 5.6. Your shutter speed will be____?

5. Indicated shutter speed: 30. Indicated f/stop: 5.6.
You wish to change your shutter speed to 60. Your f/stop will be____?

6. Indicated shutter speed: 30. Indicated f/stop: 5.6.
You wish to change your shutter speed to 250. Your f/stop will be____?

7. Indicated shutter speed: 125. Indicated f/stop: 16
You wish to change your shutter speed to 500. Your f/stop will be____?

8. You have a variable focal length (zoom) lens marked 1:4. You know this means the widest the aperture can open is f/4.
Indicated shutter speed: 30. Indicated f/stop: 4. Your ISO number: 200.

You know this is too slow a shutter speed for sharp pictures ot a volleyball game. You need to gain faster ISO speed, at least three stops. The ISO speed you would choose to obtain that:____.

9. Choosing the ISO number you indicated above, what will be your new shutter speed at f/4?
F/stop_____. Shutter speed_____.

10. You have a zoom lens marked 1:5.6.

Your light meter indicates a shutter speed of 250, f/stop 8. Your ISO: 800. You wish to lower your shutter speed to 30, to add a swirl of colored movement in a Zumba class. Describe two things you can do.

11. You want to photograph people on the street, and know that you have to work quickly. Focus may be a problem, so you need to set your camera for maximum depth of field. Which setting would be best?

a. Aperture f/4.

b. Aperture f/11.

c. Aperture f/5.6

d. Shutter speed 60.

12. You want to photograph a basketball game, and need to stop fast action. Which setting would work best?

a. Shutter speed 60.

b. Shutter speed 15.

c. Shutter speed 500.

d. Aperture f/16.