Measuring Color

We're using a new test to measure the range and consistency of colors that printers produce, using an internationally developed standard called CIE Lab, which defines color numerically. Each letter in the word Lab refers to a value: The L value indicates how light an object's color is; the a value indicates where an object's color falls on a red-to-green scale; and the b value indicates where an object's color falls on a yellow-to-blue scale.

We began by using Adobe Photoshop 3.0 to produce pages with solid blocks of cyan, magenta, yellow, red, green, and blue from each printer. We then set the Macintosh-based Colortron colorimeter, from Light Source Computer Images (Larkspur, CA), on the colored output (taking readings at five sp ecific points of three sheets per color) to determine the Lab values of these test pages. By plugging these values into a formula, we arrive at a score reflecting each printer's ability to consistently reproduce individual colors. We arrive at a second score that indicates the gamut, or the range, of colors each printer can produce.

Of the four color laser printers we tested, our results indicate that the Xerox 4900 Color Laser Printer reproduces colors the most consistently. The Tektronix Phaser 540 reproduces the largest range of colors.

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Colortron Colorimeter

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The Colortron colorimeter, from Light Source Computer Images.