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In the following quote, an "apertal ratio" of "1 ⁄ 24" is calculated as the ratio of 6 inches (150 mm) to 1 ⁄ 4 inch (6.4 mm), corresponding to an f /24 f-stop: In every lens there is, corresponding to a given apertal ratio (that is, the ratio of the diameter of the stop to the focal length), a certain distance of a near object from it ...
The depth of field, and thus hyperfocal distance, changes with the focal length as well as the f-stop. This lens is set to the hyperfocal distance for f /32 at a focal length of 100 mm. In optics and photography, hyperfocal distance is a distance from a lens beyond which all objects can be brought into an "acceptable" focus.
The image-plane illuminance is directly proportional to the area of the aperture, and hence inversely proportional to the square of the lens f-number; thus ; for constant lighting conditions, the exposure is constant as long as the ratio t/N 2 is constant. If, for example, the f-number is changed, an equivalent exposure time can be determined from
Thin lens equation f = lens focal length; x 1 = object distance; x 2 = image distance; r 1 = incident curvature radius; r 2 = refracted curvature radius
For example, the photographer may prefer to make his sunny-16 shot at an aperture of f /5.6 (to obtain a shallow depth of field). As f /5.6 is 3 stops "faster" than f /16, with each stop meaning double the amount of light, a new shutter speed of (1/125)/(2·2·2) = 1/1000 s is needed. Once the photographer has determined the exposure, aperture ...
The depth of field, and thus hyperfocal distance, changes with the focal length as well as the f-stop. This lens is set to the hyperfocal distance for f /32 at a focal length of 100 mm. In optics and photography, hyperfocal distance is a distance from a lens beyond which all objects can be brought into an "acceptable" focus.
Say you have a 4-year-old Labrador named Comet — with the new equation, Comet's real "dog age" would be slightly older than 53. The reason for the difference is actually pretty simple.
For full-frame 35 mm-format cameras, the diagonal is 43 mm and a typical "normal" lens has a 50 mm focal length. A lens with a focal length shorter than normal is often referred to as a wide-angle lens (typically 35 mm and less, for 35 mm-format cameras), while a lens significantly longer than normal may be referred to as a telephoto lens ...