Process for producing pre-press color proofs

A method of preparing a pre-press proof of an original subject having highlight, midtone and shadow tone areas using color print paper wherein the dyes of the print paper have been brought into substantial color compliance with the yellow, cyan and magenta process inks to be used in producing a lithographic reproduction of said original subject, and the tonal range of the proof image has been extended to closely match that of the final process ink print, said method comprising the steps of:

• preparing yellow, cyan and magenta color half tone separation negatives and positives of the original subject to be reproduced;
• separately placing the halftone negatives in sequential order over a sheet of color print paper sensitive to green, blue and red light respectively;
• exposing the print paper sheet to light passed through a blue filter when the yellow halftone separation negative is over the print paper sheet, a red filter when the cyan halftone separation negative is over the print paper sheet, and a green filter when the magenta halftone separation negative is in place thereover,
• said exposure of the print paper sheet being carried out with each halftone separation negative in place over the print paper sheet for a predetermined time period sufficient to cause the dyes of the print paper sheet upon development thereof to exhibit densitometer readings wherein through a blue filter, the yellow reading of the exposed print paper relatively closely matches the yellow reading obtained by densitometer measurement through a blue filter of the yellow process ink, through a green filter the magenta reading of the exposed print paper relatively closely matches the magenta reading obtained by densitometer measurement through a green filter of the magenta process ink, and through a red filter the cyan reading of the exposed print paper relatively closely matches the cyan reading obtained by densitometer measurement through a red filter of the cyan process ink;
• during exposure of the print paper sheet to light through a red filter while the cyan halftone separation negative is over the print paper sheet, also exposing the print paper sheet to light through a green filter for a sufficient period of time to cause the dyes of the print paper sheet upon development thereof to exhibit a densitometer reading wherein the magenta reading through a green filter relatively closely matches the magenta contaminant reading obtained by densitometer measurement through a green filter of the cyan process ink,
• during exposure of the print paper sheet to light through a green filter while the magenta halftone separation negative is in place over the print paper sheet, also exposing the print paper sheet to light through a blue filter for a sufficient period of time to cause the dyes of the print paper sheet upon development thereof to exhibit a densitometer reading wherein the yellow reading through a blue filter relatively closely matches the yellow contaminant reading obtained by densitometer measurement through a blue filter of the magenta process ink;
• and
• increasing the tonal range of the color print paper proof by also placing on the print paper sheet when the magenta separation halftone negative is associated therewith, the magenta halftone separation positive, and the yellow halftone separation positive on the print paper sheet when the yellow halftone separation negative is associated with the print paper sheet, and the cyan halftone separation negative on the print paper sheet with the cyan separation halftone positive, and in each instance passing additional light through the red, green and blue filters respectively for time periods sufficient to progressively extend the tonal range of the highlight and midtone areas of the film proof without unduly affecting the shadow tone area thereof.