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Preparing PDF for electronic distribution
November 28, 2007

When a document is being prepared for electronic distribution as a PDF, it’s important that it be in RGB color throughout. This is true because a majority of desktop printers in consumer and office environments are RGB printers – not PostScript – so they don’t convert color well from CMYK to RGB and then back again.

Back again, you say? Epson’s ink-jet printers, for example, are at-heart RGB devices. If you send CMYK data, they first convert the CMYK into RGB by the simplest (read: unsophisticated) means, then convert that RGB into the necessary color set for the inks in that particular printer. It’s better to send RGB data in the first place.


These desktop printers often have only CMYK inks, while the top-of-the-line Epsons have eight colors of ink (actually a dramatically expanded CMYK gamut; they achieve it with eight containers of ink and eight print heads). Canon’s new professional printers have 12 colors of ink (C,M,Y,K, Photo Cyan, Photo Magenta, Red, Green, Blue, Matte Black, Gray, and Photo Gray) and must make the conversion of color information in the printer from its preferred space – RGB – to these colors on-the-fly, and that’s no small feat.



If you think about it, the need for RGB as input to these ink-jet printers is obvious. No normal CMYK process takes light-light-gray or light cyan into account. The onboard processors on these machines make those decisions as the jobs are printed.

Here is the scheme for making pure-RGB documents with Adobe Distiller or InDesign: Whatever combination of source color exists in the document – CMYK, grayscale, RGB, Lab – convert it at the time of creating the PDF into RGB using a single ICC profile appropriate to the audience and the image quality. If the destination is expected to be primarily office printers, then it’s smart to use the rather small sRGB color space. If your audience is professional graphic arts practitioners or photographers with nicer printers, it is smart to use the more accommodating Adobe RGB 1998 profile, which will result in a much nicer appearance for those who appreciate the effort.

In Acrobat Distiller (or InDesign’s Adobe PDF Presets menu), choose Output, then select Convert to Destination Color, and include the profile. The resulting PDF will be forced to RGB color (this also works with grayscale if you need it). Once it’s complete, you can post this PDF online, and those who download it will be better able to print it on desktop and small office printers.

Posted by Brian Lawler on November 28, 2007 | Comments (0)