Ed #3 > text

Size Matters

Small—and random—is good. As anyone who has used fine screens knows, the smaller the dot, the sharper the resolution. More dots capture more of the data found in the original image, which in turn equals more apparent detail.

Stochastic screens carry that idea to the extreme. Done right, the small dots of stochastic screens can create a look that comes close to the continuous tones of a photograph. That makes them particularly well suited for handling fine lines, small sizes of type—especially when reversed out of a dark background—and high resolution images. This ability to capture more detail, especially when compared to conventional 150-line, or even 175-line, screens, is often considered to be the greatest advantage of stochastic techniques.

But small dots bring other advantages too. Small dots require less ink than the larger dots used in conventional halftone printing, which means that the film of ink applied by the press is more even. And because the ink film is thinner, more light is reflected back to the eye, especially when a bright, reflective, white paper, our premium-grade is used. Printed images can begin to gain the luminous depth of a transparency. In theory at least, small dots also mean that the ink dries faster too, which can save time on-press, get the job into the bindery more quickly, and reduce the need to use spray powder to prevent pages from sticking together. In reality, however, most printers notice little if any improvement.

If small is good, random may be even better, because it helps to eliminate several types of troublesome moirés—the distracting, wavy patterns that sometimes appear in printed images. While they can’t be seen on monitors, moirés can cause big problems on press. Subject moirés appear when the image that is reproduced includes grid or line patterns—such as those found in fabrics or fences—that clash with the pattern of halftone dots on conventional ruled screens. Screen angle moirés appear when halftone screens are placed at too shallow an angle to avoid interfering with other screens, one of the biggest reasons why printing jobs in more than four colors using conventional techniques can be a challenge. Scan moirés occur when the size of the image is changed and a pattern in the original image interferes with the rigid grid of pixels in the scan.