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Holography Glossary


  • Aerial perspective - the distance or depth effect caused by atmospheric haze. Haze creates a large amount of extraneous ultra-violet light to which all photographic emulsions are sensitive.
  • Acetic acid - chemical used for stop baths and to acidify acid fixing solution.
  • Acetone - solvent chemical used in certain processing solutions that contain materials not normally soluble in water.
  • Albumen paper - printing paper invented by Blanquart-Evrard in the mid-19th century where egg whites were used to coat the paper base prior to sensitization. The albumen added to the brightness of the white base and substantially improved printed highlights.
  • Allegory - work of art that treats one subject in the guise of another. An allegoric photograph usually illustrates a subject that embodies a moral "inner meaning".
  • Alum - chemical used in acid hardening fixing baths.
  • Aluminum compounds - groups of chemicals often used as hardeners in fixing baths.
  • Ambrotype - Mid-19th century photographic process introduced in 1851-52 by Frederick Scott Archer and Peter Fry. It used weak collodion negatives which were bleached and backed by a black background which produced the effect of a positive image.
  • Amidol - soluble reducing agent which works at low pH values.
  • Ammonium chloride - chemical used in toners and bleachers.
  • Ammonium Dichromate - chemical used as a sensitizer in Dichromated Holograms.
  • Ammonium persulfate - chemical used in super-proportional reducers.
  • Ammonium sulfide - pungent but essential chemical in sulfide or sepia toning.
  • Ammonium thiosulfate - highly active fixing agent used in rapid fixing solutions which works by converting unused silver halides to soluble complexes.
  • Amphitype - Mid-19th Century process based on an underexposed albumen-on-glass negative. This was viewed by reflected light against a black background to give a positive image similar to a ambrotype.
  • Anaglyph - result of forming stereoscopic pairs from two positives each dyed a different color, usually green or red.
  • Antiscreen plates - photographic plates containing dyes that reduce the blue sensitivity. Used unfiltered, they can give results similar to those obtained with yellow filtered orthochromatic plates.
  • Apodization - lens treatment designed to cut down diffraction fringes that appear around the images bright points of light.
  • Aquatint - etching technique allowing control of tonal areas to produce almost unlimited gradations from pale gray to black. Because of this it has also been used in photography as an alternative term for gum bichromate process.
  • Argentotype - Mid-19th century silver print process, on which the kallitype and sepia paper processes are based.
  • Aristotype - early commercial print type made on collodion-chloride or gelatin-chloride paper.
  • Azo dyes - compounds forming colors of great strength and purity. Used in camera filters and integral tripack dye-bleach materials.