Methods for determining printer adjustments to accommodate proof/print substrate color differences
View Patent ↗Embodiments of the present invention provide systems and methods for adjusting for differences between a proof substrate and the ultimate substrate on which an illustration or other image is to be printed. Embodiments are particularly useful for any print process on an opaque substrate where a proof representing the expected result is provided that has a different substrate color or value from that being used in the print process.
1. A method for determining adjustment to an output of a color printer to account for color differences between an image provided on a proof substrate and the same image printed on a final print substrate, comprising:
(a) measuring the print substrate in order to determine a specific spectral or colorimetric value of the print substrate;
(b) measuring the proof substrate in order to determine a specific spectral or colorimetric value of the proof substrate;
(c) converting each spectral or colorimetric value obtained from (a) and (b) into a CIE XYZ value;
(d) converting each CIE XYZ value into CIELAB values, such that there is provided a CIELAB value of the proof substrate and a CIELAB value of the print substrate;
(e) calculating the change between the CIELAB value of the print substrate and the CIELAB value of the proof substrate;
(f) inputting the change obtained from step (e) into the color printer such that the color printer adjusts tone reproduction, allowing an image printed on the substrate to substantially match color values of an image printed on the proof substrate.
2. The method of claim 1 , wherein step (e) uses the formula:
CΔ=((bp−bs*−1)*z/yn
MΔ=((ap−as)*z)/yn
YΔ=((bp−bs)*z)/yn
KΔ=((Lp−Ls/2)*z/2.5
Tonal A between the proof substrate and the print substrate=
IF(tonal range <=xb,−tonal range,
IF(tonal range >=xe,100−tonal range,
IF(ymax<=((100−xmax)+(100−xe))/2,
IF(tonal range <=xmax,a0*tonal range*tonal range+b0*tonal range+xb,a1*tonal range*tonal range+b1*tonal range+c1),
IF(tonal range <=xmax,a0*tonal range*tonal range+b0*tonal range+xb,
IF(tonal range <=x1,a2*tonal Δ range*tonal range+b2*tonal range+c2,a3*tonal range*tonal range+b3*tonal range+c3))
where;
tonal range=tonal range of print substrate
xe=tonal range max
xb=tonal range min
x1=(200−xmax−2*ymax+2*c2*xe*(xe−xmax))/(2*c2*(xe−xmax)+1)
ymax=ΔY
xmax=max Δ
a0=−(xb+ymax)/((xmax−xb)*(xmax−xb))
a1=(100−xe−ymax)/((xe−xmax)*(xe−xmax))
a2=−(2*c2*(xe−x1)+1)/(2*(x1−xmax))
a3=(xmax+ymax−100)/(2*(xe−xmax)*(xe−xmax))
b0=−2*a0*xmax
b1=−2*a1*xmax
b2=−2*a2*xmax
b3=−1−2*c2*xe
c1=ymax+a1*xmax*xmax
c2=ymax+a2*xmax*xmax
c3=c2*xe*xe+100
n=0.7
y=n*(n*sl)*0.3
sl=−0.3
xn=1.6
yn=1.2
z=(n^y/xn)*1
p=proof
s=press substrate color
L=L value obtained from CIELAB calculation
a=a value obtained from CIELAB calculation
b=b value obtained from CIELAB calculation
THEN Tonal Δ+printing device values=calculated amount of change between the CIELAB value of the print substrate and the CIELAB value of the proof substrate.
3. The method claim 1 , wherein measuring the print substrate and measuring the proof substrate are conducted using a spectrophotometer.
4. The method of claim 1 , wherein inputting the change further comprises adjusting the tone scale reproduction of the printer so that a color reproduction of the image printed on a final print substrate resembles the tone scale and color balance of the image provided on the proof substrate.
5. A method for adjusting an electronic output system of a press or color printer so that a final print closely resembles an image of a proof provided in hard copy on a proof substrate or on a video monitor, comprising:
(a) measuring the proof substrate or calibrated monitor virtual proofing white point; and
(b) applying logic to adjust the tone scale reproduction of the printer so that the color reproduction of the printed image resembles the tone scale and color balance of the hard copy or monitor based proof.
6. The method of claim 5 , wherein the measuring the proof substrate or calibrated monitor virtual proofing white point comprises measuring the substrate color of the hard copy print or measuring the color of the monitor or virtual proof substrate by adjusting the tone reproduction of the printer or press in a complementary manner so that the printed image resembles the color of the monitor or virtual proof image.
7. The method of claim 5 , wherein the applying logic to adjust the tone scale reproduction of the printer comprises adjusting at least one of the tone scale or color reproduction or both for the printer according to algorithms that produce tone scale and color modifications.