G CURVE

Definition: Is an average gradient of a characteristic curve, describing similar characteristics to gamma, but measuring the slope from a line joining the lower and upper of the curve actually used in practice.

Definition: The average gradient of a characteristic curve, describing similar characteristics to gamma, but measuring the slope from a line joining the lower and upper limits of the curve actually used in practice.

G4 COMPRESSION

Definition: A compression technique used in Fax Group 4. It produces very good results for black and white, and is frequently used as an option in TIFF files for black and white images. It is also used in Adobe Acrobat (PDF) files.

GAIN

Definition: A method of adjusting a CCD sensor's sensitivity to light.

GAIN & LEVEL

Definition: Gain and level are image processing terms which roughly correspond to the brightness and contrast control on a television. The gain is the " contrast " and the level is the "brightness". By changing the level the entire range of pixel values are linearly shifted brighter or darker. Gain on the other hand linearly stretches, shrinks the intensity range, thus altering the contrast.

GALVANOGRAPHY

Definition: technique of electroplating a gelatin relief image created photographically to produce a photomechanical printing plate.

GAMMA

Definition: The contrast affecting the mid-level grays or midtones of a image. Adjusting the gamma of an image allows you to change brightness values of the middle range of gray tones without dramatically altering the shadows and highlights.

Definition: measurement used in sensitometry to describe the angle made between the straight line portion of the characteristic curve of the photograph emulsion and the base of the graph. The gamma is the tangent of the angle so formed.

GAMMA CORRECTION

Definition: The measure of contrast that results in lightening or darkening the midtone regions of an image. Also, the amount of midtones need to be adjusted on a monitor.

GAMUT

Definition: The range of colours and tones a device or colour space is capable of recording or reproducing. The human eye can sense many more colours than can be reproduced on a computer monitor in RGB colour space.

GAMUT COMPRESSION

Definition: The editing of an image to reduce the colour gamut so that the image can be displayed or output within the limits of a particular device.

GAMUT MAPPING

Definition: The plotting of an image colour gamut into the CIE colour space.

GANGING

Definition: Putting a group of images or jobs on the scanner or press at one time.

GATEWAY

Definition: A computer server that allows for the connection of different computer network using protocol conversions.

GAUSSIAN BLUR

Definition: An image softening effect utilizing a bell shaped gaussian distribution to apply the softening effect.

GCR

Definition: Abbreviation for gray component replacement; the separation technique where black ink is used to replace either a portion of the unwanted component in a saturated colour, or a combination of cyan, magenta, and yellow equivalent to the unwanted component. Typically specified to improve colour control on older presses.

GELATIN

Definition: natural protein used as a transparent medium to hold light sensitive silver halide crystals in suspension, binding them to the printing paper or film, yet swelling to allow entry of processing solutions.

Definition: A substance produced from animal skins and bones, it is the basis for modern photographic emulsions. It holds light-sensitive silver halide crystals in suspension.

GELATIN FILTER

Definition: Are filters cut from dyed gelatin sheets and held in front of the lens or studio light.

GELATIN FILTERS

Definition: filters cut from dyed gelatin sheets and held in front of the lens or studio light.

GELATIN SUGAR PROCESS

Definition: daylight printing process using paper with a sugar and dichromate coating, which hardens on exposure to light.

GENERAL PROTECTION FAULT ( GPF )

Definition: A general protection fault error message occurs when an application tries to write to memory that is not designated by the operating system.

GENERATION LOSS

Definition: The loss of quality that occurs in any type of analog duplication such as an interneg. Digital images do not have this kind of loss of quality when duplicated.