6 HOW the camera controls light
SNAPSHOT
- Understanding Aperture and F stops
- Understanding Shutter and Shutter speeds
The camera controls the amount of light entering it in two ways, the aperture and the shutter.
Aperture
The lens of the camera has an opening called the aperture. The size of the aperture can be adjusted by rotating a portion of the lens (mechanical cameras), or by turning the command dial (electronic cameras) when it is in aperture mode. You will know you have found the correct dial for changing the aperture when you see more or some of the following numbers: 2, 2.8, 4, 5.6, 8, 11, 16, 22. These numbers are called f stops, and indicate the size of the opening.
The bigger the opening the more light will enter the camera, making your image brighter. Although it gets a little confusing, because the bigger the number, the smaller the opening….go figure!
For example, f 16 is a small opening and therefore will not let in a lot of light. This might be a good setting for shooting outdoors in bright light. f 2.8 is a big opening and lets in a lot of light. This might be a good setting for shooting indoors.
To make it even more confusing, your camera lens may not have all these numbers and if you have an electronic camera you may have additional numbers in between the numbers shown above. Your manual will be helpful here.
Shutter
Because the aperture is always open, light is always coming into the camera….however it gets stopped from touching the film by a curtain that is called the shutter.
The shutter curtain is always closed protecting the film from the light coming in through the aperture. What happens when you push the shutter release button?…If you guessed that the curtain opens, you were right!
As soon as the curtain opens, the light coming in from the aperture will expose the film for as long as the shutter stays open.
Shutter speed
There is a dial on your camera that allows you to set the time for how long the shutter will stay open. The longer it stays open the more light will get on the film. 
To locate the dial that controls the shutter speeds, look for these numbers: 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000.
These numbers represent fractions of a second. 1 is really 1/1 (one second) and 2 is 1/2 (half of a second), 4 is 1/4 (a quarter of a second), etc. As the numbers get bigger, the time the shutter stays open gets shorter.
For example, a shutter speed of 60 (which is 1/60th of a second ) will let more light in than a shutter speed of 500 (1/500th of a second).
If you are in a situation with low light, you will need to keep the shutter open longer, to let more light in, and you will want shorter times if you are in bright sun.
- Set the aperture to f 5.6 and the shutter to 125, now change that to Aperture f 8 and shutter to 15, f 16, and 250………. You’re getting the hang of it. if you are using a mechanical camera you need to use the film advance lever, after you click the shutter, even if you don’t have film in the camera. The camera does not allow you to take a second picture without doing this in order to prevent accidental double exposures.
KEY TAKEAWAYS
- Aperture controls the quantity of light entering the camera
- F stop is the measurement of the aperture or lens opening
- Shutter controls how long the light hits the film
- Shutter speed is the speed with which the shutter opens and closes
Aperture is the adjustable lens opening that controls the amount of light allowed into the camera.
Shutter or shutter curtain is a shield in the camera protecting the film from light. It is right behind the film plane.
The length of time the shutter(curtain) stays open during exposure. The photographer sets the desired time using the shutter speed dial
Film exposure is the amount of light that passes through the camera lens and reaches your film over a period of time. (Light x time) Exposure determines how light or dark your image is.
A command dial or camera dial is a dial used on cameras to change the camera's mode.
f stop is the measurement of the aperture/lens opening
Shutter or shutter curtain is a shield in the camera protecting the film from light. It is right behind the film plane.
