Hand coloring is a process of applying color tints, in the form of paint, to a photographic image to create or enhance the color effect. Hanger is a frame for holding sheet film for processing. Hard defines a scene, negative or print with high contrast. Hardeners are chemicals often used with a fixing bath to strengthen the physical characteristics of an emulsion. The most common hardeners are potassium or chrome alum.
Hard gradation is a term denoting the quality of harsh contrast in a photograph.
Heat filter is an optical attachment made of thick infrared absorbing glass, used to absorb heat radiation from alight source without diminishing output. Heliography is an early photographic process invented by Niepce, employing a polished pewter plate coated with bitumen of Judea. Helmholtz, Hermann 1821-1894. German physicist who worked with Young in developing the Young-Helmholtz theory of color vision. Herschel effect is the destruction of an exposed image by infrared radiation.