Simulating Printer Colors: Monitor Differences
We found that no matter what engine or printer we use, selecting the function, 'Simulate Printer Colors,' reduces the size of the gamut measured on the monitor. The HP Color Laserjet printer profile reduced the gamut significantly more than either the Adobe Illustrator Printer Default printer profile or the Kodak DS 1000 PS Clear Film printer profile, however, suggesting worse color resolution on the monitor. While the Adobe Illustrator Printer Default profile reduced the gamut less than the Kodak DS 1000 PS Clear Film profile, the difference between the two was not substantial.
In all cases, however, it is obvious that the function, 'Simulate Printer Colors,' shrinks the RGB monitor gamut in an attempt to model the CMYK colors of the printer.
Adobe CMS
Kodak Digital Science
ICC CMS
When we convert our measurements into Lab space, it becomes obvious that the HP Color Laserjet printer profile affects the monitor colors the most. While our gamut comparisons seemed to show that the Adobe Illustrator Printer Default profile changed our monitor colors the least, however, the Lab space comparison clearly and more accurately proves that the Kodak printer profile has the smallest effect. No matter what printer profile we choose, however, blue is the color most effected by simulating printer colors. It is drastically distorted in all cases, while the CMYK colors are only slightly different, if they are modified at all.
Adobe CMS
Kodak Digital Science
ICC CMS
Our Lab comparisons also show that the engine
choice does not have much of an effect on our monitor color display.
The delta E values for each printer with each engine seem to correlate
more strongly with the printer profile than with the print engine.
Simulating Printer Colors: Monitor Colors vs. Printout Colors
Comparing our monitor gamuts to our printout gamuts is very useful once the imperfect illuminant has been converted to a D65 white light. In all cases it is obvious that the 'Simulate Printer Colors' gamut measured on the monitor is subjectively closer to that of our printouts.
Adobe CMS
Kodak Digital Science
ICC CMS
In Lab space, we can get a better picture of our situation. When we plot the delta E Lab difference between our monitor's original colors and the printout's colors and compare it to that of our monitor's simulated print colors and the printout's colors, we consistently find that the monitor's simulated print colors setting is closer in Lab space to our final product than are the monitor's original colors.
Adobe CMS
Kodak Digital Science
ICC CMS
Determining which setting most closely matches our printer's output is not difficult. When we compare the average Lab space differences for each setting, we find that the HP Color Laserjet printer profile along with the Adobe Default Engine most closely matches our printer's output colors.
RGB to CMYK Conversion
We also converted a strictly RGB gamut to CMYK in Adobe Illustrator using their "RGB-->CMYK" function. Regardless of the engine, the Red, Green and Blue chromaticity values shrink into the CMYK color space. This is evident in the gamut plots. When we convert into Lab space, we discover that the Green and Blue components actually get closer to their final printout level, which is expected since our printer colors are CMYK. Overall this function has the effect of matching the RGB space more closely to the CMYK space of the printer as is evident by the uniform error after the function has been run.
RGB to CMYK
With Printout Gamut
Lab Space
CMYK to RGB Conversion
Next we converted a CMYK gamut to RGB in Adobe using the inverse of the function described above. The gamuts do not line up as well. When we convert to Lab Space, we see that the Cyan, Magenta, Yellow, and Black components all get closer to the printer output level as we convert to RGB. Since the error reduction is the same for each color it appears that we are merely shrinking the CMYK space and not warping it to match the RGB space. This is to be expected since we are measuring the output of a printer. So the CMYK to RGB conversion is not as effective as that of going the opposite direction.
CMYK to RGB
With Printout Gamut
Lab Space