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Glossary: G

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Gain (image)
In practical discussions of digital cameras and scanning devices, gain is described as a means of increasing the ISO of the device and apparent sensitivity to light. In more technical terms, gain in a digital imaging device represents the relationship between the number of electrons acquired on an image sensor and the analog-to-digital units (ADUs)…
This term has slightly different meanings in conventional photography and in digital imaging; this definition pertains to the latter. The human eye has a nonlinear response curve (it is more sensitive to variations in low light than to equal variation in bright light). In order to present viewers with images that look natural or…
See Gamma correction
Gamma correction
Gamma and gamma correction have to do with bridging the difference between linear representations of the intensities of light and the nonlinear response of the human eye, which is more sensitive to variations in low light than to equal variation in bright light. Gamma correction is an image processing operation that compensates for the…
See Gamma
The range of colors that can be generated by a specific output device (such as a monitor or printer), or can be interpreted by a color model. Often referred to as color gamut.…
See Also Color; Color model
Geometric distortion
See Distortion, Geometric
The Graphics Interchange Format (GIF) is an 8-bit-per-pixel bitmap image format. The format produces images that are small and efficient through the use of a limited 256 color palette and of the Lempel-Ziv-Welch (LZW) lossless data compression scheme. GIF is widely used for graphics with areas of solid color such as maps, illustrations,…
Gray card
A gray card is used as a reference point for assisting to determine the exposure of objects in reflected light. Gray cards normally reflect 18% of the light falling on them. Ideally, gray cards are designed to be spectrally neutral and produce a diffuse reflection. Often times the alternate side of…
An image type lacking any chromatic data, consisting of shades of gray ranging from white to black. Most commonly seen as having 8 bits per pixel, allowing for 256 shades or levels of intensity.…