Picture It: How do cameras handle light?

How do changes in aperture size and shutter speed affect the photograph?

The main component vital to any good photograph is light. Cameras are designed to process light in fractions of a second to produce the beautiful photographs we see today. Light passes through the lens on the camera or an opening for light to pass through, projecting an inverted image onto the film. You can adjust the amount of light by changing the size of the opening at which light passes as well as the open time. Using a digital camera or making a pinhole camera we can observe the effects of these changes through the images produced.

• Digital camera with manual settings: f-stop control and shutter speed.

• Pinhole camera
• Light-tight container: oatmeal box, coffee can, shoe box, etc. Use your imagination!
• 35mm camera film
• pin
• scissors
• electrical tape
• black paint (spray paint or acrylic paint)

The following procedure is for digital cameras.

1. Set your camera to a manual setting. You should be able to control the f-stop and shutter speed.
2. Choose your subject and setup a tripod or on a table so that the camera is in the same position for every photo. Choose an area where their is moderate light. Not too dark or too bright.
3. Start by setting the camera aperture to f/5.6
4. Set your shutter speed to 1/250s.
5. Take an image.
6. Record the exposure number along with the shutter speed setting and aperture in a chart (Figure 1).
7. Repeat, setting your shutter speed to 1/125s, 1/60s, 1/30s, 1/15s,1/8s, 1/4s, 1/2s, 1s.
8. Set your shutter speed to 1/125s.
9. Set your aperture to f/2.8.
10. Take an image.
11. Record the exposure number along with the shutter speed and aperture setting in a chart (Figure 1). Repeat, setting the aperture to f/4, f/5.6, f/8, f/11.
12. You can repeat steps 9-12 but change the shutter speed in step 8.
13. Load your photos onto your computer.
14. Using your exposure number chart rename the image with its shutter speed and aperture setting. ex. "1-125, f2-8". Use dashes if your program does not allow you to use names with "/" or ".".
15. Graph your results (Figure 2).

a) Changes in shutter speed

b) Changes in aperture size/f-stop.

Figure 1. Data chart with aperture and shutter speed settings for each image.

Figure 2. Graph of the amount of light with respect to shutter speed.

Terms/Concepts: Exposure; f-stop; shutter speed; How do film cameras work?; How do digital cameras work?

References:

• http://wwwca.kodak.com/global/en/consumer/education/lessonPlans/pinholeCamera/pinholeCanBox.shtml​
• http://www.youtube.com/watch?v=qnnHjz8pF1M&feature=related