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 colours). This keying to singular grey- or colour values is known in modern image processing as
using L.U.T.s. The fact that a certain density of a photographic layer has been caused by a specific amount of
actinic radiation (visual light, UV-light, X-Rays, autoradiography, etc.) can be used to qualify and perform spatial measurements of a physical phenomenon. A calibrated photographic process is used to obtain quantitative measurements as well. Equidensitometry with Agfacontour made it possible to obtain reproducible equidensities similar to pseudosolarized photographic films and prints. The Agfacontour film contained two special emulsions with each different spectral sensitivity. Using color filters (yellow or magenta) during the exposure on Agfacontour one could control the width of the equidensity. By varying the exposure one could change the density in the image that showed on Agfacontour as equidensity. Although the material exhibited very low sensitivity (long exposures were necessary) the results were very reproducible and second order equidensities were sharp and clear, something that with pseudosolarization was almost impossible to achieve without special procedures. In the following fields equidensitometry is used extensively: • Photoelastic Stress Analysis, using polarized light and birefringent models of the object under test. •
Radiology (
Mammography and other low contrast images of organs and bones File:Flash continuous tone image.jpg|Flash against white wall File:1st. order equidensity of a flash image.jpg|Flash against white wall, equidensities serie of the first order (sandwiching several equidensities transparencies) File:XRay R hand print.jpg|X-Ray image of right hand with no details in the bones at the bottom of the image File:XRay R hand with 1st. order equidensities.jpg|Original: X-Ray image of right Hand;1st. order equidensities after pseudo-solarization of original File:X-Ray_image_of_right_hand;_colored_equidensity-series_using_pseudo-solarization.jpg|Original: X-Ray image of right hand;colored 1st. order equidensity-series using pseudo-solarization, B&W copies chromogenic developed ==See also==