Group shows which fail to establish a legitimate theme cheat both the artist and the viewer. For the gallery, they are an easy alternative to making a commitment to an individual photographer - the safety in numbers theory. If the gallery owner or the museum curator doesn't have a strong candidate for a one-person show, he can fall back on the group exhibit. The thinking is, "I'll hit with one if I don't hit with them all." And that the critics will find something that will please them. This is unfair to the photographers, since a good artist can be lost in a crowd of the less talented, or attention drawn only to one controversial person or work.

A group show usually allows five to 10 prints per photographer, making it difficult for a photographer to present himself fully or to be judged fairly by so few prints.

It is also unfair to the viewer, who takes the time to go to an exhibit, and gets only a smattering of impressions of any one artist. If you are lucky you'll find something to suit your taste in this smorgasbord, and maybe you'll buy it. Then the gallery owner gets lucky.

The Lunn Gallery has employed a shotgun approach to its large group show. More than 50 photographers are represented on the two floors of its Georgetown Gallery. The gallery, which is known for its collection of antique photographs, has managed to thinly represent 125 years of photographic history. Indeed, the show is graphic history. Indeed, the show is a walking tour of the history of photography, but one with a strange bias. The masters are all here, but the pictures for which they are known are not exhibited. Indeed, the gallery seems to have gone out of its way to pick offheat and noncharacteristic work for some of the photographers. There is an Ansel Adams picture, "Taos Pueblo," dated 1929. When you think of Adams, you think of his marvelous scenics from the mountains and the desert. They are close to perfect, a joy to study and to own. But the Lunn Gallery has chosen an awkward, uncharacteristically contrasty photograph which might have historic value but has little aesthetic value.

The great photojournalist Henri Carter-Bresson, who coined the expression "the decisive moment," is also there. He is a remarkable photographer whose composition and timing are his trademark. The Lunn Gallery has chosen to exhibit an out-of-focus, 1948 news picture made during Gaudhi's funeral. The picture is unlike anything associated with Bresson's fine work.

This raises the question as to why these and other pictures were selected. The gallery says the show was drawn from its annual catalog, which this year features photography exclusively. The viewer is left to conclude that there are a lot of famous photographers whose every piece of work is not worth a place on a gallery wall.

The Sander Gallery, which opened less than a year ago, sits atop an ice cream parlor. The bright, well-lit show rooms are pleasant to visit. Sander has had one-person shows in the past, but offers a six-photographer show this month.Instead of building a show around a theme, it simply has hung six very diverse artists together and called the show, appropriately, "Photographers at the Gallery."

Conceivably the exhibit could have been built around the work of Larry Fink, who photographs parties, among other things. Parties, like colds, are common to the lives of most of us, and are therefore very difficult to shoot well, since everyone presumably already knows about them. Fink succeeds very well. The viewer is left with an eerie, deja vu feeling. Here are people you know and a situation you can identify with - only the conclusion to the familar story is unknown.

The other five photographers in this fine if disjointed show are Peterhans, Dearstyne, Chargesheimer, von dem Bussche and Riebesehl.The show closes March 5.

The Washington Gallery of Photography has done well at solving the group show problem. They have a major show of George Tice work in their front room and two other photographers shown in a separate room. Everybody has room to breathe with this arrangement.

One of Tice's exquisite trees greets the visitor in the front window. It and other trees, plants, waterfalls and waterways are among his strongest images. Tice's show is a retrospective exhibit of about 20 years of work. A show such as this can add to the glory of an artist by clearly demonstrating his maturity or it can be his downfall by calling attention to less memorable work. Tice walks the tightrope between these two extremes easily and well. His early work invovled portraits of his family, of the Amish and of rural blacks. Later he concentrated on his lovely trees and their environment. More recently he documented Paterson, N.J.

A sense of loneliness pervades all of Tice's work, and his people look lonely even in groups. His interiors, particularly the barber shop (1970) and the men's room (1975), have a nostalgic air. Late afternoon sun filters into the rooms which were recently populated but now look as though they have been abandoned for all time. His exteriors are reminiscent of our childhood or imagined childhood neighborhoods.

This hopping and skipping through Tice's creative development is fun and entertaining, but Tice is at his best when he presents one portfolio, one theme or one project at a time.

Keeping Tice company, but from a distance, is the work of two University of Maryland students. Paul Gasparola's deep, rich prints favor rocks, water and trees. Jack Teemer presents several abstracts and nudes and three mysterious pictures all containing ruber gloves.

The Washington Gallery of Photography will be closing its doors soon at its Capitol Hill location at 216 7th St.

Mary Schumaker, co-owner with her husband, Byron, a former Washington. Star photographer, would say only that the couple are moving to their country place in Rappahannock County, Va. They are moving themselves but not the photo gallery, she indicated, although she didn't rule out the possibility of a relocated gallery later.