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How to Find Aperture Diameters

The aperture is the opening inside of your camera lens that allows light to enter into the camera and expose a photograph. On many single-lens reflex cameras and digital SLRs, the aperture is easily adjusted by rotating the aperture ring, which is usually located on the lens. The actual diameter of the aperture will vary from lens to lens, depending on the focal length of each camera. Therefore, it is necessary to make some simple calculations to determine the diameter of the aperture for each individual lens.

Instructions

- 1
  Locate the focal length of your lens and write it down on a piece of paper. The focal length is usually written on the end of the lens and will be measured in millimeters. Refer to the camera or lens manual if you cannot locate the focal length on the actual lens.
- 2
  Examine the back end of the lens where it meets the camera to find the aperture adjustment ring. Look for the "F" numbers, as apertures are frequently referred to as f/stops. Write down the aperture setting of your camera.
- 3
  Divide the focal length of your lens by the aperture setting to determine the diameter of the aperture. For example, a lens with a focal length of 50 mm and an aperture of f/2 will have a diameter of 25 mm.

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