Color Printing

In the past, producing color prints at home required a darkroom, access to running water, good temperature control through a multi-step process, a good enlarger with a three-color head, and lots of patience and money. Now, inexpensive color printers are available that produce color prints equalling or exceeding the quality of photographic prints. Epson led the field with introduction of its six-color printer model 1200 printer years ago. This has been followed with improvements in drop size (giving greater resolution) and very large gains in image stability (from a meager six years to "archival" with projected print lifetimes of seventy-five years or more) as a result of development of pigmented inks, which are now incorporated even in Epson's bottom-line printers. The current six-color printer is based on the standard CMYK primaries--cyan, magenta, yellow and black--but adds two more, a low-density cyan and a low-density magenta. These low density primaries allow the deposition of a larger number of ink drops to render low-density images, which, accompanied by very small dot size (4-6 picoliters), provides sharp and almost grainless prints.

Theoretically, an image that looks beautiful on the screen ought to look beautiful as a print. I'm sure many readers have had the unfortunate experience of getting a muddy, dark or off-color print from such an image. One should bear in mind that the viewing conditions for a print and for a screen image are quite different and have a large effect on perceived image brightness. Usually the print will appear darker than the screen. Viewing conditions also affect color perception and are likely to vary more for the print (which can be viewed in daylight or in artificial light-- tungsten or fluorescent--than for the screen image. Also important is proper calibration of the viewing screen; some screens, particularly CRT's, have built-in calibration routines to assure correct color reproduction.. For critical work, LCD screens that have a narrow acceptance angle are a "No No" because image contrast varies too much with viewing angle.

But perhaps the greatest offender in producing off-color images is a poorly calibrated printer. This is more likely to be a problem with inexpensive, non-OEM ink cartridges or with refill inks. I have made the practice of periodically checking printer calibration by printing a continuous gray scale (a gray image that runs from total transparency to a very dark black*). If the gray scale prints a color other than black, the printer cannot produced a balanced color print. The result of this test can be used to make adjustments to the screen image (using an image-editor such as Photoshop) to achieve balance. For example, a scale that prints with a red cast will require a decrease in red image component (i.e., an increase in cyan). After each such adjustment, a trial gray scale print is made and adjustments continued in this fashion until an acceptable printed gray scale is achieved, at which point, the total adjustment required to balance the gray scale is applied to the final image to be printed.

Beyond color balance, I use an image editor to adjust contrast and exposure. With the Olympus E10, I find an increase in contrast of 10-15% is required to add some "snap" to the image. Proper use of the "Levels" tool in Photoshop (and Photo Elements) can be applied to adjust exposure. I routinely sharpen every image before printing; the process that translates a camera image into CMYK printing coordinates does so by averageing groups of neighboring pixels with concomitant (if small) loss of sharpness. Sharpening must be done tastefully; over-sharpening leads to unpleasant artifacts such as white outlines around sharp edges and can yield an unnatural ("unphotographic") appearance.

*A gray scale can be conveniently prepared in Photoshop or Photo Elements by setting foreground color to black, background color to white, and dragging the Gradient Tool from top to bottom of a designated square on the screen.

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