I’m hoping someone can help me with the following problem.
I’m trying to tint the paper to match the white of the mat
board. My issue is figuring out the exact, specific sequence to
accomplish this without lots of trial and error.
I have created several test prints and things just don’t seem to
come out the way I expect. With all the instrumentation available today,
surely there’s got to be a simple and straight-forward way to accomplish
this. I mean, what’s the point of all the multi-thousand dollar
instruments, profiling software, etc., if color matching is still just trial
and error?
Here’s what I did. Please correct me if I’m wrong:
1)
Measure paper white of the mat board with a
Spectrophotometer. I’m using the Spectrolino with Gretag Measure
tool. For this particular mat board, I get LAB = (95.1, 0.6, -0.1)
2)
Measure paper white of the print paper. For
this particular paper, I’m getting (91.4, 0.3, -1.9)
3)
Determine the difference (paper – mat) = (-3.7,
-0.3, 1.8)
4)
Open a new document in Photoshop with the corresponding
printer/paper profile.
5)
Edit > Fill with the above color (paper –
mat). Photoshop only accepts whole numbers for LAB colors so everything
must be rounded to the nearest integer value.
6)
L: Since L is negative (paper is already
darker than the mat board), so L should stay at 100.
7)
b: Since a* can be rounded to 0, no a*
correction is needed.
8)
b: I need a tint of 2 (1.8 rounded) in the b
axis to offset the -1.9 paper color.
9)
LAB: So, I should aim to set the value to (100,
0, 2)
So, I go to the Photoshop Color Picker and enter LAB values of
100,0,2. This show the corresponding RGB value of (255,255,255) which
tells me that 100,0,2 is not a distinguishable color for this
printer/paper. However, if I enter RGB values of 255,255,250 to
255,255,248, then LAB values show 100,0,2. (Perhaps this is a bug in
Photoshop Color Picker).
So I printed a color patch of 255,255,249 – right in the middle
of the above values. Then I measured the result. But the color
still reads the same as the paper white.
So, I figure that there’s got to be a way to do this without
creating a test print of all the possible RGB combinations and then measuring
the output to find the right match, and then repeating that for every type of
paper/printer that I use.
Ideas?
Michael