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Base curve radius (BCR) or simply base curve (BC) is the measure of an important parameter of a lens in optometry. On a spectacle lens, it is the flatter curvature of the front surface. On a contact lens it is the curvature of the back surface and is sometimes referred to as the back central optic radius (BCOR). Typical values for a contact ...
In photography, exposure is the amount of light per unit area reaching a frame of photographic film or the surface of an electronic image sensor.It is determined by shutter speed, lens f-number, and scene luminance.
At moderate exposures, the overall shape is typically a bit like an "S" slanted so that its base and top are horizontal. There is usually a central region of the HD curve which approximates to a straight line, called the "linear" or "straight-line" portion; the slope of this region is called the gamma. The low end is called the "toe", and at ...
Extended exposure time of 26 seconds. Exposure value is a base-2 logarithmic scale defined by (Ray 2000, 318): = = , where N is the f-number; and; t is the exposure time ("shutter speed") in seconds [2]
Radius of curvature (ROC) has specific meaning and sign convention in optical design. A spherical lens or mirror surface has a center of curvature located either along or decentered from the system local optical axis. The vertex of the lens surface is located on the local optical axis.
Also may mean "Perspective Control" for a lens that has the ability to shift to tilt to control linear perspective in an image. May also stand for personal computer in conjunction with digital photography. PDAF: Phase-detection autofocus. One of the mechanisms of automatic lens focusing. PF: Purple fringing. A form of chromatic aberration in ...
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Many steps in the process of photography are recognized as having their own nonlinear curves, which in combination form the overall tone reproduction curve; the Jones diagram was developed as a way to illustrate and combine curves, to study and explain the photographic process. [4] [5]