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Holography Glossary


  • Galvanography - technique of electroplating a gelatin relief image created photographically to produce a photomechanical printing plate.
  • Gamma - 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.
  • Gelatin filters (gells) - filters cut from dyed gelatin sheets and held in front of the lens or studio light.
  • Gelatin sugar process - daylight printing process using paper with a sugar and dichromate coating, which hardens on exposure to light.
  • Ghost images - bright spots of light, often taking the shape of the aperture, which appear in the camera viewfinder or in the final photograph when a lens is pointed at a bright light like the sun. Ghost images have been almost eliminated through the use of multi layer coatings of the lens elements.
  • Glaze - glossy surface produced on some (non resin coated) printing papers. It is achieved by placing a wet print to to a heated drum or clean polished surface. Glazed print produce denser medium blacks than their matte counterparts.
  • Gold chloride - soluble chemical used in gold toners.
  • Gold mean - compositional technique used to determine the "ideal" position of the main subject in the frame. It is based on creating a rectangle from a square. A line drawn from the center of one side of the square to the opposite corner becomes the radius of an arc. The side of the square is then protracted until it meets the arc, and from this point a rectangle is constructed. The side of the square which remains in the rectangle indicates the point at which the subject should be placed.
  • Gray card - card with an 18 percent gray tint (reflectance) used to determine exposure by taking a meter reading from subject light reflected by the card.
  • Greenies - Slang, These are often found in DCG processing and appear as a green blob in the image.
  • Gum arabic - water soluble gum obtained from the Acacia tree and used in coatings of a number of photographic processes.
  • Gum bichromate - contact printing process once very popular for the manipulative, impressionistic effects it makes possible. Drawing paper is coated with a mixture of gum, potassium bichromate and a pigment of any chosen color. This is then exposed to light behind a negative. Also known as the photo aquatint process. Gum platinum process - combination of gum and platinum printing.