![]() ![]() With Dynamic Area AF, you can select from several focusing options: 9-, 21- or all 51-point AF. With good light control and a static subject, Single Point AF ensures that the most important element in the composition, such as the eyes in a portrait, will be sharply focused. Nikon's three AF Area Modes-Single Point AF, Dynamic Area AF and Auto Area AF-are designed to handle any shooting situation. This is handled by material (glass) selection, shape and positioning. It is impossible to eliminate them all, but in the lens design process, they can be controlled and balanced to provide the best possible result for that lens and application. In addition, there are also two types of chromatic aberrations, which are caused by more than one frequency. The five most common types in aberration are SEIDEL's five aberrations, which occur even with monochromatic (single-wavelength) light. In reality, however, light refraction by the lens causes a variety of defects in the image, called aberration. the object and the image (on the film or imaging sensor) must closely resemble each other. when the object plane is perpendicular to the optical axis, the image plane must also be perpendicular and 3. all light from the point object must be focused to a single point on the image plane (film or digital sensor) 2. The ideal image by lenses (especially photographic lenses), must fulfill three key conditions, namely, 1. To provide that speed, a Nikon proprietary technology called overlap servo prepares for the focus detection of the next shot while the lens-driving operation for the current shot is in process.Īn aberration prevents light from being brought into sharp focus. To realize high-precision AF for high-speed continuous shooting of a fast-moving subject, the processing speed of the AF cycle is vital. The AF modules built into selected Nikon D-SLRs have as many as 51 focus areas that can detect vertical, horizontal and diagonal movement of the subject. ![]() Simple predictive tracking is very effective for pictures of a subject moving at constant speed toward the camera, but to provide maximum focusing performance for a subject that abruptly changes direction at high speed, or a subject with low contrast, moving randomly, the AF system must accumulate subject location data using multiple focus areas. The prediction is based on a measurement of the subject's movement and speed. To solve this problem, the focus tracking system is a predictive system that uses special algorithms to forecast the position of the subject at the moment the image is captured. However, maintaining focus doesn't guarantee a sharp image, as there is a short time lag between the release of the shutter and the capture of the picture. With the shutter release pressed halfway, you'll see in the viewfinder the lens continuously maintain focus as the subject moves. An invaluable feature for sports, action and wildlife photography, 3D focus tracking, available in select Nikon D-SLRs, automatically shifts the focus point to follow the movement of the subject. ![]()
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