THE SOFTNESS of Clara Sipprell's portrait photographs dates them. It brings to mind the Photo-Secessionists and Alfred Stieglitz, the innovative photographer Sipprell sought to emulate in the 1920s. It was a style she liked, and she stuck to it for her 50-year career, as can be seen in a show of 33 of her photographs at the Portrait Gallery.

The soft touch. In her softly focused photographs (she preferred portraits), the air surrounding her subject is almost visible. The dreamy effect works well in her photograph of Robert Frost at 81. Hale and hardy, the poet sits on one of the mending walls he could never fathom. Sipprell captures Grandma Moses, also in her later years, as an appealing sprite with a sparkle.

Authors, artists, musicians and statesmen posed for her camera, as well as ordinary people who just wanted nice family portraits. Here are contemplative images of Duncan Phillips, of Nelson Rockefeller at 22, of Pearl S. Buck, of Felix Frankfurter and Oliver Wendell Holmes.

At one time Sipprell's photos, using whatever light happened to be in a room, were very au courant -- appearing in Vanity Fair and House Beautiful. But then documentary photography became the preferred style. And perhaps the flash, and other developments, outshined such simple effects as available light.

Sipprell was a formula photographer. The gallery's Sipprell collection -- a recent bequest of Phyllis Fenner, her close friend -- numbers almost 600. But the photos not displayed here are more of the same, simple and contemplative, with the same flattering soft focus -- and no surprises.