Photographs Worth a Double Take.

FOR much of its history the camera has been regarded by most of its users as a reliable recorder of visual experience. But professional photographers, especially those who use the medium to make art, have always known better. ''A photograph is a secret about a secret,'' Diane Arbus said. ''The more it tells you, the less you know.'' When Allan Chasanoff, a New York art patron and photographer, began building a photography collection more than two decades ago, it was this idea, about the subtle deceitfulness at work in even the most straight-ahead snapshot, that guided him. It propelled him to look for imagery, by photographers both famous and decidedly less so, that he came to categorize as ''the optical'' -- not trick photographs, but more or less conventional ones that opened a ''a crack in the realism screen,'' as he wrote, pictures that you look at, then have to look at again (and again). [ABSTRACT FROM PUBLISHER]