Printing black text is fairly straightforward: Any given spot on the paper either has black pigment on it or does not. To get smoother edges or higher resolution, many laser printers adjust the size and even the position of the black dots on the image grid by modulating the laser beam.
Producing photographic images is more complicated because the printer must create the illusion of gray shades by tiling varied groups of black dots called
dithering patterns
. The gray shades come at the expense of resolution, but, again,
laser modulation can help
, either by making dithering patterns less obvious or by squeezing more gray shades from a smaller pattern. The production of dithering pattern
s is even more complicated with color images, because clusters of the four process colors (cyan, magenta, yellow, and black) must imitate various hues.
Both Tektronix and Apple have developed methods to effectively coerce more colors from smaller dithering patterns. By modifying the laser beam's pulse duration to give some pixels more or less energy than others, the printer's electronics affect how many ultrafine toner particles adhere to a each pixel. The result: several intensity levels for each color instead of all or none.
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Squeezing Colors from Pixels
