![]() ![]() The f-stop setting (the aperture size) affects depth of field smaller apertures (larger f-stop numbers) increase the depth of field. ![]() diaphragm numbers, and Kodak's 1-2-3-4 scale (There is usually an inverse correspondence between the lens's smallest f-stop number and its price.)į-stop scale, U.S. The "faster" a lens, the smaller its smallest f-stop number fast lenses for 35mm cameras may be f/1.8, f/1.4 or even f/1.2. All of the following combinations would result in the same exposure on film: This makes it simple to adjust exposure by selecting shutter speed and f-stop combinations: for example, going from f/11 to f/8 has the same effect on exposure as going from 1/250 second to 1/125 second. To make things a little easier, it turns out that each f-stop (the numbers shown above) lets in twice as much light as the next higher one, and half as much light as the next lower one. Some lenses only go down to f/16, while other lenses (such as the larger lenses used on view cameras) may go down farther, to f/22, f/32, f/45 or even to f/64. Typically, the smallest f-stop will be something like 2 or 2.8 for a 35mm camera lens from there, the normal marked progression is 4-5.6-8-11-16-22. A lens is said to be "wide open" when it's set on its smallest f-stop, or with the aperture opened as wide as possible. The f-stop number is a ratio of the focal length of the lens to the diameter of the aperture. Confusingly, the f-stop number increases as the aperture gets smaller, letting in less light. ![]() The measure of the aperture setting on a lens. ![]()
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