THE SHOW is called "Peter Costas, a Photographer for Sixty Years." If you love photography as an art form, or are just mildly interested in taking a few snapshots now and again, let me urge you to rush down to see this very special exhibit.

If you pride yourself on your technical know-how, don't miss this show.

If you love to look at special, one- of-a-kind cameras and the pictures they produced, they're here for the viewing. If you want to see examples of custom mural prints, this is the place.

The exhibit is at the Walker, Ursitti & McGinniss Gallery in Northwest D.C. and will run through February 16.

The leading element in this remarkable show is Costas' use of the "fisheye" lens. He was a pioneer in the use of super-wide-angle lenses, building cameras to do jobs never done before. Now, at 78, he continues to search for the perfect picture.

The first thing you see as you enter are two 4-by-4-foot sepia- toned fisheye prints, one of the Capitol and the other of the Arlington Cemetery amphitheater.

The amphitheater picture may be the most successful fisheye ever made. The curves of the stone benches and the bowl shape of the arena itself fit precisely into the format of the lens.

The Capitol picture is a perfect example of 180-degree photography. Costas has photographed himself standing beside the camera.

At the other end of the room is a cluster of nine 10-by-10-inch fisheye views of such Washington landmarks as the National Gallery of Art and the Lincoln and Jefferson memorials, as well as one of the Costas' home in Anacostia. They blend into a Washington potpourri, but each picture bears study by itself.

Along with the fisheye views, there are some fine telephoto and special-effects pictures.

Most extraordinary of these is "Wide-Angle Capitol." It's in color and was taken with a camera Costas invented and calls the "Wide O Rama." It uses roll, not sheet, film. The picture shows the entire Capitol building, from Senate to House, with almost no distortion.

The print is four feet tall and 13 feet wide.

Then there are the 8i-by-10i black-and-white news pictures: a 1935 shot of a street in Southwest and some candids of John F. Kennedy. They are hard-hitting and reveal Costas' news picture work.

You'll want to spend some time looking at the collection of Costas' original, hand-built cameras, especially the one with a compartment on top to hold a sandwich.

The printing, by Washington House Photography, is really fine. The Capitol Hill mural is as good as any print that size I've ever seen.

The gallery, at 457 M Street NW, is open Wednesday through Sunday, noon to 5, or by appointment. Don't be put off by the lack of a sign. Just walk up and ring the bell.