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Exposure

Exposure. In order for an image to be captured, it must be exposed to light. The camera uses two things to control the amount of incoming light (a.k.a. exposure): Shutter Speed Aperture (F-Stop). Shutter Speed.

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Exposure

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  1. Exposure

  2. In order for an image to be captured, it must be exposed to light. • The camera uses two things to control the amount of incoming light (a.k.a. exposure): • Shutter Speed • Aperture (F-Stop)

  3. Shutter Speed • Shutter speed controls the amount of light let into the camera by the length of time it remains open. • In a film camera, 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. You can control the length of time the shutter remains open by changing the settings - the SHUTTER SPEED.

  4. Before taking a look at how digital cameras control exposure, it helps to understand how a film camera does the job. When the camera isn't in use, the shutter is closed, preventing light from reaching the film. When you take a picture, the shutter opens, and light hits the film.

  5. Shutter speed:Determines HOW LONG the shutter stays open. • Examples: • A half second exposure is ONE STOP darker than a one second exposure. • A 1/125 exposure is TWO STOPS brighter than a 1/500 exposure. • The longer shutter speed (like 1 second) the MORE light to reach the photo. The shorter the shutter speed (1/1000) the less light to reach the photo. So even though the number may look bigger, don't be deceived!

  6. Slow Shutter Speed Photos

  7. Fast Shutter Speed Photos

  8. Aperture • Aperture is the second thing that controls the exposure of a photo. • Aperture is the size of the opening in the lens of the camera (go back to the previous slide which shows the film camera). The larger the aperture opening, the more light there will be to expose the photo during the shutter speed. The aperture opening is in front of the shutter on a camera.

  9. The aperture settings on most lenses (called f-stops), run in a series from the largest to smallest opening: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16 and f/22 are the most common. The higher the f-stop number, the smaller the lens opening.

  10. Aperture Photos Look at the photos to the left. Notice that as the F-Stop number goes up, the photo gets darker. This is because the aperture opening gets smaller.

  11. When you combine Shutter Speed and F-Stop together, you get a photo’s EXPOSURE. • To find the proper exposure you have to find the right combination of shutter speed and aperture openings in each particular lighting situation. • This is done through the Law of Reciprocity. • I am also including a “General Exposure Guide” with this lesson. Print it off and bring it with you to take pictures. The Exposure Guide has a list of starting points for Shutter Speed and F-stop (depending on weather). This might help you when you are away from your computer.

  12. Law of Reciprocity Definition • RECIPROCITY LAW– The reciprocity law states that Exposure = Intensity X Time. “Intensity” is the amount of light (aperture), and “Time” refers to how long that amount of light is allowed to act on the photo (Shutter Speed).

  13. Law of Reciprocity • Basically, it means that there is a relationship between length of the shutter speed and intensity of light (F-Stop). An increase in one setting will be balanced by a decrease in the other.

  14. Guides:1000 – F 4500 – F 5.6250 – F 8125 – F 1160 – F 1630 – F 22 • The reciprocity law therefore means that an exposure provided by ƒ8 and 1/250 sec will give the similar results as ƒ11 and 1/125 sec., and so on. If one choice of settings provides proper exposure, then the others will as well.

  15. Exposure Project • Photographers often use a technique called "Bracketing" their exposures as a form of exposure insurance. Bracketing is a deliberate over and under exposure of the film in an attempt to secure the optimum exposure. Once the initial exposure has been made, the photographer might change one or both of the exposure controls (aperture and shutter speed) to insure an ideal exposure.

  16. Exposure Project • This week you are to take daylight pictures of a subject of your choice. Pick a scene with even light. (Keep all the Elements of Composition in mind to create an interesting and unique photo!) • Make all your exposures from the same spot (if you have a tripod you could use it here). Be sure to write down your exposures for every frame (Shutter Speed and F-Stop)!

  17. SS: 100 F-Stop: 4.5 SS: 100 F-Stop: 5

  18. SS: 100 F-Stop: 9 SS: 100 F-Stop: 18

  19. SS: 100 F-Stop: 25

  20. SS: 50 F-Stop: 6.3 SS: 100 F-Stop: 6.3

  21. SS: 200 F-Stop: 6.3 SS: 400 F-Stop: 6.3

  22. SS: 800 F: Stop: 6.3

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