Explain Camera Lens F-Stop
The f-stop setting an a single lens reflex (SLR) camera lens determines how much light enters the camera through the lens. Also called the aperture setting, the f-stop value is one of the key components to achieving a well exposed photograph. If the image is too dark, or too light, the f-stop will need to be adjusted to allow more or less light to enter the camera.
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F-stop and Exposure
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Gaining a proper exposure can be boiled down to the simple equation, exposure = shutter speed + aperture (or f-stop). The shutter speed regulates how long light enters the camera, while the aperture, or f-stop setting, determines how wide the aperture ring opens in the camera to allow the light in.
Effecting the Image
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Controlling the exposure, specifically the brightness and darkness, is partially a result of the f-stop or aperture setting on the camera lens. A smaller f-stop number indicates the aperture ring is open wide. A larger f-stop number means the aperture ring in the lens is closed down, or "stopped down", which allows less light into the camera.
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F-stop Examples
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Photographing a dimly lit situation may require the use of a large aperture, or f-stop number such as f2.8 or f4.0. If the scene is very bright with sunshine, the lens will need to be stopped down to f16 for example, so the camera sensor or film plane isn't flooded with too much light. This would result in an overexposed (too bright) photo.
Maximum Aperture
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Look at the barrel of the lens attached the film or digital SLR camera. A range, or maximum f-stop number, will be listed with the focal length of the lens. Each lens has a limit on how wide the aperture ring can open. Purchasing a lens that allows for a wide aperture of f1.2 or f2.0 is much more costly than a lens with a maximum aperture of f3.5 or f5.6.
Meaning of F
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Debates continue as to why the aperture setting on a camera lens is referred to as the f-stop. Focal length, focal ratio and focal have all been discussed as the meaning of the f in f-stop.
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References
- Photo Credit Orin Zebest, Flikr/Creative Commons
