After numerous test prints, I have made some progress...
Image enhancement: ON
Image Quality: Enhanced
Color Correction: none
RGB Color Correction: none
(everything else at default)
With these settings, the print picks up the various shades and shadows of the green field background, and detail is nearly identical to the PCL6 output. However, the print is quite under-saturated.
Any of the methods for "Color Correction" (Automatic, sRGB Display, sRGB vivid, LCD) badly distort the background (i.e.. The green field becomes a couple of shades of green). The people in the foreground look decent. So leaving this setting at "none" seems to be required.
Using "RGB Color Correction" methods of "Perceptual" or "Relative Colorimetric" produce a good print, but still not as good as the PCL6 print. The shadows and details of the green background are not as pronounced as the PCL6 print...still a little too green. The faces of the people in the foreground are a bit red...maybe the print is still a bit oversaturated.
Also, RGB profile of "Adobe 1988" seems to help a bit.
I'm not sure what else to do at this point. I don't see a way to set up custom color correction profiles. I need to increase saturation for the no color corrections options, or slightly decrease saturation (possibly) for "Perceptual".
Any suggestions are welcome!
I've been able to get excellent quality photo/image prints from the Phaser 6180 using the PCL6 driver in Windows XP from various software programs (using "Enhanced" image quality and "Photo" image type).
However, I'm trying to use the printer from an Ubuntu Linux 12.04 LTS system with the CUPS driver from the Xerox website, and the photo quality is rather poor. The photo/image prints are grainy, and there is no distinction between subtle variations in color (for example, a field of green grass will have a very uniform green color, where there should be various shades of green).
I've tried various options in the PS print settings for image enhancement, quality, screen etc. (there are many options), and have not found anything that helps. In fact, it often seems that changing the print settings has little to no effect on the printer output.
I went back to Windows and played with the Postscript driver, and was able to make some improvements, but was still not able to obtain results that were as good as those from the PCL6 driver.
Does anyone have any suggestions on how to improve the quality using the CUPS driver? Is there a PCL6 driver available for Ubuntu/Linux? I've been reading on the various settings in the PS driver, but I likely don't have a good understanding of what effects they have, or how they interact together.