Printing to Desktop Printers
The way Photoshop prints to a desktop printer depends on the color mode in which it expects to receive data. Photographic printers are true RGB devices—they expose photosensitive paper using red, green, and blue lasers or LEDs—so the CMYK color mode simply doesn't apply. Inkjet printers use cyan, magenta, yellow, and black inks (plus additional inks to extend gamut and detail), which in theory at least makes them CMYK devices. But in practice, unless you're printing through a PostScript raster image processor (RIP), desktop inkjet printer drivers are built to receive only RGB data. This is because traditionally, operating system-level graphics languages have not been able to send CMYK to printers. Photoshop itself can send CMYK to these printers, but the printer driver will immediately convert it to RGB before doing anything else with it.
A PostScript RIP may seem to allow more control over the printing process by letting you control the individual inks, but that usually isn't the case. PostScript RIPs that use the printer's native screening algorithms usually send RGB to that part of the print process; those that truly provide ink-level control use their own screening, which may not look better than the printer's native screening. A PostScript RIP makes sense from a workflow standpoint if you're using a desktop printer as a proofer for prepress, but if your desktop print is your final output, use your printer's own RGB driver or a specialized RIP designed for photo output, such as Colorbyte's ImagePrint.
RGB Output. If you're printing RGB, you can skip the entire CMYK section in this chapter. You should, however, read the sections "Choosing an RGB Working Space," "Soft-Proofing Other Color Spaces," and "Converting Colors When You Print" carefully. We recommend using ICC profiles for your printer. If you print using the printer vendor's inks and papers, the canned profiles that come with the printer may work well. If you're using third-party inks and papers, though, a custom profile will improve your output immensely. Inexpensive scanner-based profiling packages such as the PANTONE huey can work well with inkjet printers and can pay for themselves in savings on ink and paper. Don't use your RGB printer profile as an RGB working space, because RGB printer spaces aren't gray-balanced or perceptually uniform, making editing difficult. Instead, use a working space such as ProPhoto RGB, and fine-tune your image for output using Proof Setup to create a simulation of the printed output.
CMYK Output. If you're printing CMYK through a PostScript RIP, almost everything we say in this chapter about press CMYK applies equally to desktop printers.