Patent ID: 7321448

Claim:
A color proofing method for improving the color reproducibility of printed matter to be produced by a printing press in proof print produced by a proof press, the color proofing method comprising the step of: correcting proof printing image data, in which each of levels of monochromatic color gradation of black on the printed matter is represented on the proof print, out of the proof printing image data over the entire color space in a subtractive process resulting from color matching between proof print produced by the proof press and the printed matter to be produced by the printing press in such a manner that a part having a black ink area factor of 100% on the printed matter is represented only with black ink also on the proof print, but that a part other than the part having a black ink area factor of 100% on the printed matter is represented on the proof print by using under color removal, to thus reproduce, on the proof print, the representing characteristics of the black ink on the printed matter; and, wherein the step of correcting the proof printing image data includes the steps of: finding min(C 100 , M 100 , Y 100 ) from color values (C 100 , M 100 , Y 100 , Bk 100 ) of the proof printing image data for representing, on the proof print, the part having the black ink area factor of 100% on the printed matter, to thus determine a new value P of Bk 100 ; finding an addition value α 100 for Bk 100 in accordance with the following equation: α 100 =min( C 100 , M 100 , Y 100 )×( P−Bk 100 )/min( C 100 , M 100 , Y 100 ), wherein 1≦P≦100; adding the addition value α 100 to Bk 100 as well as setting all of C 100 , M 100 and Y 100 to 0; and repeating, with respect to n from 99 to 1, the following steps of: determining min(C n , M n , Y n ) from color values (C n , M n , Y n , Bk n ,) of the proof printing image data for representing, on the proof print, a part having a black ink area factor of n % on the printed matter; determining an addition value α n with respect to Bk n in accordance with the following equation: α n =(min( C n , M n , Y n )−(100 −n ))×( P−Bk 100 )/min( C 100 , M 100 , Y 100 ), wherein 1≦P≦100, to thus add the addition value α n to Bk n ; and obtaining respective reduction values β n , γ n , δ n of C n , M n and Y n in accordance with the following equations: β n =α n ×(( P−Bk 100 )/ C 100 ), γ n =α n ×(( P−Bk 100 )/ M 100 ), and δ n =α n ×(( P−Bk 100 )/ Y 100 ), wherein 1≦P≦100, to thus subtract the reduction values β n , γ n , and δ n , and C n , M n and Y n , respectively.