Calibration method for video image reproduction with electronic printer and video monitor

Claim 1

A video image reproduction system comprising: a video image printer; a video monitor; means for applying a video image to said video image printer to reproduce said video image in photosensitive medium and to said video monitor to display said video image on said monitor; and means for correction said applied video image on a pixel-by-pixel basis so that said video image displayed on said monitor and said image reproduced in said medium have a uniform quantization in perceived lightness, such that the perceived grey scale varies linearly with video image signal value; wherein said video image printer is a cathode ray tube multiformat camera; wherein said cathode ray tube multiformat camera (CRT MFC) includes brightness, contrast and density controls and wherein a first look-up table is generated as follows: printing a set of gray scale test patterns on film by means of said CRT MFC at preselected contrast and density control settings C 0 and D 0 and at incremental brightness settings B 1 , B 2 , B n ; measuring the density of film with a densitometer to determine the maximum film density, D max , for each brightness setting; from a plot of B vs. D max , selecting a desired D max and finding the brightness control setting B' to give the desired D max ; causing said CRT MFC to print on film the same said gray scale test pattern using brightness, contrast and density settings, respectively, of B', C 0 and D 0 ; with a densitometer, measuring the film density for each gray level and calculating intermediate densities using an interpolation technique; converting the set of density values into perceived lightness values using the formula S.sub.f =c.sub.1 (10.sup.-D.spsb.f).sup.p +c.sub.2 where c 1 and c 2 are normalization constants, D f is film density, and p≈1/3; constructing said first look-up table from the measured and desired tone curves; wherein said monitor has brightness and contrast controls; and wherein a second look-up table is generated as follows: varying said brightness and contrast controls of said monitor to obtain, using a photometer, a desired minimum luminance, L min , and maximum luminance, L max , which correspond to minimum digital image value, CV=0, and maximum digital image value, CV=2 n -1, respectively; using a photometer, measuring the monitor luminance for each level of said gray scale test pattern used in constructing said first look-up table; calculating said monitor luminance for other digital image values, CV, using an interpolation technique; converting the monitor luminance values L m into perceived lightness values S m , using the visual perception characteristic formula S.sub.m =c.sub.1 (L.sub.m).sup.p +c.sub.2 where c 1 and c 2 are normalization constants and p≈1/3; and constructing said second look-up table from the measured and desired tone curves.