Camera Aperture

"The eye of the camera."

The aperture is a diaphragm opening that controls the opening of the lens through which light enters the camera (much like the iris of an eye). By controlling the opening, it controls the way that the picture will look.


The settings of an SLR aperture are called f-numbers or f-stops. The standard sequence is f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. As the numbers get larger the opening gets smaller and lets in its ratio to the number above or below it. Example,...f/8 lets in twice as much light as f/16, and f/2 lets in half as much light as f/1.

Depth of Field

This opening's main influence over the appearance of a photograph is its control over the depth of field. As the opening gets smaller and smaller, the depth of field gets larger and larger.

If the goal is to have only the subject in focus with the foreground and background out of focus, a lower setting is desirable. If more of the scene needs to be in focus, a larger setting needs to be used. This will affect your exposure, so the shutter speeds will have to be matched up so your picture does not get over or under exposed.

These settings and the shutter settings are what determine your exposure (the total amount of light that hits your film or image sensor).


If the picture is focused the way that was intended but the picture is too dark, change your shutter speed to allow light in longer. If the same picture is too bright, increase your shutter speed to keep it open for a shorter amount of time. This will take some practice but you can get some cool effects by experimenting with exposure and depth of field.

Use the Preview

Most cameras do not adjust the aperture to the chosen setting until just before the picture is taken. Because of this, the picture taken may not look the same as the scene in the viewfinder. To get around this, most SLRs have a preview option that will adjust the opening to allow you to see what the picture will really look like. Be sure to check your camera's owner's manual to find out how to use the preview option.

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