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Glossary
G
Gelatin:
a substance produced from animal skins and bones, it is the basis
for modern photographic emulsions. This holds the light-sensitive
silver halide crystals in suspension.
Glossy:
describes a printing paper with a great deal of surface sheen.
Opposite: matte.
Graded-contrast
paper: printing paper that
produces a single level of contrast. To produce less or more contrast,
a change has to be made to another grade of paper. See also: variable-contrast
paper.
Graininess:
in an enlarged image, a speckled or mottled effect caused by oversized
clumps of silver in the negative
Gray
card: a card that reflect
a known percentage of the light falling on it. Often has a gray
side reflecting 18 percent and a white side reflecting 90 percent
of the light. Used to take accurate reading (meters base their
exposures on a gray tone of 18 percent reflectance) or to provide
a known gray tone in color work
Ground
glass:
1) a piece of glass roughened on one side so that an image focused
on it can be seen on the other side. 2) the viewing screen in a
reflex or view camera
Guide
number: a number used to
calculate the f-setting (aperture) that correctly exposes a film
of a given sensitivity (film speed) when the film is used with a
specific flash unit at various distances from flash to subject.
To find the f-setting, divide the guide number by the distance
Gum
bichromate process: an
early photographic process revived by contemporary photographers.
The emulsion is a sensitized gum arabic solution containing color
pigments. The surface can be altered by hand during the printing
process. Also called gum dichromate.
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