The aperture controls the amount of light that reaches a digital camera sensor. An aperture acts much like the pupil of an eye. It opens wider as light decreases to let in more available light. It gets smaller when light increases to reduce the amount of light entering the eye.

The combination of aperture and shutter speed are related, and effect the exposure value. The faster the shutter speed, the larger the opening of the lens and visa versa.


Camera F StopsThe diameter of an aperture is measured in f-stops. A lower f-stop number opens the aperture and admits more light onto the camera sensor. Higher f-stop numbers make the camera’s aperture smaller so less light hits the sensor.

When an aperture is opened up by one f- stop, the amount of light which reaches the sensor is doubled. F-stops are expressed in three different ways: f/8, f-8, and 1:8.

Aperture settings can be used creatively to control depth of field, how much of a photo is sharp in front and back of where you focus on the main subject.

Using a wide aperture (small F-stop number) is a desirable technique for many close-up and portrait shots.

Aperture Priority Mode

All digital cameras have exposure modes that automatically control the aperture and shutter speed. But many allow you to manually change the aperture.

When using aperture priority mode, change the aperture and the shutter speed is automatically changed to maintain proper exposure.

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11 Responses

  1. Gail Bjork says:

    Sushi, you can control aperture by setting a camera to aperture priority mode. However, most compact digital cameras don’t have AP mode. But it probably has a macro mode (for close-ups) or portrait mode and the camera will be factory preset to use the best aperture for the subject.

  2. Sushi says:

    how do u control the aperture in a compact digital camera if there is one? sorry if this is a dumb question but im still confused about this whole thing

  3. john says:

    you’re all very very welcome! i try my hardest to give you all the information you need. :] :]

  4. Very informative…helped me a LOT with my science fair project, thanks so much! I didn’t even understand aperture before this!! :)

  5. Gail Bjork says:

    You’ll get comprehensive help for this type of question at dpreview’s Lighting Technique Forum.

    For helpful tips, take a look at this article covering some of the technical aspects of portrait photography.

  6. Bryan says:

    I am new to portrait photography. I have a set of lights 600ws each. Just purchased a digital SLR. In making adjustments to the camera and lens 28/135is I seem confused to what my camera setting should be to get the best portrait shot. I have a light meter and the first reading with flash came at f/22 and my iso was 400. The photograph totally bleach out my first shot. Any hints when shooting a portrait as to the settings on the camera?


  7. Julia says:

    thank you ! this was very helpful (:

  8. Vanda says:

    thank you for such a helpful site especially to some just starting out with a digital camera

  9. rachel says:

    Thanks!  Informative!

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