Printing in photo quality with my Photosmart C7180 results in grossly incorrect colors in the very dark areas of the photo. The problem occurs _only_ when printing in "Photo" quality. What appears to be happening is that in the very dark area the CMYK "black" level goes out-of-range with the result that no black ink at all gets used in that area. The problem does not occur when printing in "High Quality" or "Normal" mode.
The quickest way to demonstrate the problem is to print the HP Printer Test Page to a device configured to print in photo mode: Printout Mode: Photo (on photo paper) Media Source: Photo TrayResolution,...: 1200dpi, Photo, Full Bleed, Black + Color Cartr, Photo Paper
As can be seen in the TestPage attachment, the text prints in light orange and the areas of the picture that should be dark shadows print in a garish shade of orange. (Because the picture contains a lot of orange, the error is not glaringly apparent until you compare it with a properly rendered test page.) The second attachment shows a series of printouts from Gimp applying various level corrections to an image. The picture in the upper left is the uncorrected image. The bright orange areas in the model's hair are places where Gimp indicates a CMYK "black" level of 95% or higher (compositions like C 0%, M 11%, Y 67%, K 96%). The upper right image has had the "brightness" level increased by 20%. The image at the lower right has been adjusted with a "Value" curve constructed to keep the CMYK "black" level below 80% while maintaining the original gradient in the brighter areas of the picture. These results were produced on CentOS 5 running hplip and hpijs version 1.7.2 installed from the Fedora Core 6 RPMs. An HPLIP installation from hplip-1.7.4a.tar.gz yielded identical results. (Yes, I completely uninstalled the 1.7.2 RPMs and deleted the printers first.) Connecting this printer to a Windows XP host and printing this same picture yields reasonable results. There is loss of detail in the veryy dark areas, but not the gross misrendering that HPLIP produces. So, the printer itself seems fine, and I'm not sure what is happening (integer overflow in hpijs, perhaps?). Any suggestions for a workaround would be welcomed. Carefully examining and correcting each image prior to printing is not practical. The best I can do right now is to print in "High Quality" mode on photo paper, which does work albeit with some loss of image quality as compared to "Photo" mode. -- Bob Nichols Yes, "NOSPAM" is really part of my email address.
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