A Short Course Book
Using Your Digital Camera
A Guide To Great Photographs

Exposure Controls—The Shutter and Aperture

Click to explore how exposure determines how light or dark an image is.
One of the most important aspects of photography is getting the exposure right because it determines how light or dark an image is and what mood it conveys. The two most important exposure controls are the shutter speed and aperture because both affect the total amount of light reaching the image sensor. However, they do more than just control the exposure. As you'll see shortly they are also the most creative controls you have.
  • The shutter opens to begin an exposure and closes to end it. The shutter speed setting determines how long the shutter opens to expose the image sensor.
  • The aperture is the hole through which light enters the camera. The size of the hole can be changed to control the brightness of the light that reaches the image sensor.
If you strip away all of the modern technology and look at the earliest cameras, you will find the same controls in much simpler, and perhaps easier to understand, versions.

In the early days of photography, a plate called a waterhouse stop, was inserted into a slot in the lens. The size of the stop's hole acted just like the iris apertures used today. A lens cap was removed and then replaced to begin and end the exposure—a primitive version of a shutter. This vintage camera is surrounded by waterhouse stops (apertures) and a lens cap (the shutter) leans against it.
Photo by Ake Borgstrom at www. photographica.nu.

Less light makes an image darker (left) and more light makes it lighter (right).

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