Photography is booming in popularity, and color photography -- primarily home color processing -- is one of the big reasons.

Amateurs are turning to processing their own color slides and prints because increased commercial processing costs are rising, quality from commercial labs is fleeting, and new products for the home color processor are now easier to use.

At the head of the home color processing parade is Cibachrome. Their latest addition to a wide line of color processing materials is a luxurious Pearl-Surface RC-based print paper. This new Cibachrome "A" paper is processed in Cibachrome P-12 chemistry, the same as the original Cibachrome Type A "hi-gloss" paper, which remains available. The advantage of the Pearl-Surface RC costs slightly less than the hi-gloss, carrying a suggested list price of $25.16 for a package of 20 sheets (8" x 10") or $50.25 for a package of 10 sheets (16" x 20").

With the introduction of Kodak's Type 2203 color print from slide paper, Unicolor set to work developing a compatible color chemistry. The results: RP-1000, an all-liquid kit in quarts and gallons with an optimum processing time of 13 1/2 minutes, using just three steps. Suggested list price is $14 per quart or $26 per gallon, and depletion is at the rate of 2 ounces per 8" x 10" print.

If color prints from negatives are more your pleasure, Paterson offers a new trial-size Acucolor 3. Two trial-size, two-ounce bottles combine with water to make 16 ounces of chemistry (parts A and B) to process up to eight 8" x 10" prints of Kodak Ektaprint RC or similar paper. Suggested list price for the trial size of Acucolor 3, $15.95.

To go with your print-from-negative chemicals, Paterson's new Power-Drive Thermodrum comes with paper-processing drum, water bath, three chemical-storage bottles, three color-coded graduates and a new Power-Drive motor, which operates on four 1.5-volt batteries for up to 50 processes. The Power-Drive ensures uniform processing so crucial to making color prints of good quality. Suggested list price for the Power-Drive Thermodrum, $139.90.

Finally (and without much bravado), Kodak has made some dramatic improvements in its Kodacolor 400 color negative film. It now features much better grain than previously, with overall lower contrast in the highlight areas. Also, Kodak has improved the new 400 ASA film's latent image-holding qualities. That means you can shoot the new film and have confidence that the image isn't quite so likely to deteriorate before development as in the old Kodacolor 400. The editors at Modern Photography tested the new film earlier this year and found "the easily visible grain clumping exhibited when the older film was underexposed has been almost eliminated." That means you'll end up with better prints even when you underexpose the negatives. While the new and improved Kodacolor 400 was initially introduced in 110-cartridge format, it's now available at most film outlets around the country in 35mm and 120mm sizes, as well. Q. I'm about ready to give up. Everywhere I turn, I see references to depth-of-field. I know it has something to do with image sharpness, but I'm not sure. What is it? Is it worth worrying about? A. Depth-of-field has been plaguing amateur photographers since George Eastman made his image.

In a nutshell, depth-of-field is the area in a scene that's rendered acceptably sharp on film. Say, for example, that you focus on a boy 15 feet from the camera. The depth-of-field for that scene might extend from 5 to 25 feet. That means that everything within the field from 5 to 25 feet from the camera would be rendered acceptably sharp on film. That's simple enough.

The problem comes in, though, as depth-of-field changes. It's affected by three things: the focal length of the lens on the camera; the distance from subject to film; and the size of the lens aperture in use. By changing any one of these things, you might change the depth-of-field in the example above from 5 to 25 feet to 13 to 19 feet, thus diminishing the field considerably. Or extend it from, say, 3 to 45 feet. As a rule, the closer you are to the subject, the longer focal-length lens you use; and the wider the lens aperture, the smaller the depth-of-field, and vice versa.

Say you're photographing a young lady just 6 feet from the camera, and there's a distracting tree in the background, perhaps 40 feet away. By using a wide-lens aperture, you can get an in-focus subject and an out-of-focus background, which will eliminate most of the distraction of the tree, the opposite is true, too. Let's assume you've focused on that young lady 6 feet from the camera, and you also want the background -- which might be a breath-taking panorama of the Grand Canyon -- in sharp focus. Simply use a narrow lens aperture, or switch to a shorter focal-length lens or back away from the subject.