Equidensitometry
Equidensitometry is the technique of measuring equidensities in a photographic deposit or photographic layer, such as photographic films and photographic plates. Equidensities are points, lines and areas having equal densities also called isodensities. First order equidensities are points, lines and areas having isodensities obtained by applying one of the listed below techniques once, thus they exhibit one particular Density in the original Second order equidentities are points and lines having isodensities obtained by applying one of the listed below techniques twice, thus they exhibit two particular Densities in the original. Second order equidensities do not normally show areas. Equidensity series is a sandwich (in register) of a number of different equidensities. Usually each equidensity is coded by color or raster. Photographic and computerized image processing techniques Four techniques of obtaining equidensities are: Tone separation process Sabattier effect, also called pseudo-solarization Agfacontour Professional film (discontinued) Computerized LUTs Manipulating custom curves (U-curves) in photo-editing programs such as PhotoShop provide tools to obtain equidensities in digital image processing. Applications Interpretation or measurement of an image is sometimes aided by simplification of the density pattern. This results in data reduction and enables keying (areas or lines with iso-densities to unique patterns, grey values or