BEFORE the invention of the camera, there were photograms. The Denver Art Museum brings this neglected medium up to the minute with the comprehensive ``Experimental Vision: The Evolution of the Photogram since 1919'' (through March 27).
Beautiful and mysterious, these proto-photographs captured images in light on chemically treated, light-sensitive paper without the benefit of a camera. Though the medium has been used by a spectrum of important artists from its ``reinvention'' in 1919, there have been no major historical surveys of their work in the United States until now.
The show gives a tantalizing overview of the photogram with strong emphasis on the works of key artists, beginning with the independent experiments of Christian Schad, Man Ray, Laszlo Moholy-Nagy, and Raoul Hausmann.
Moholy-Nagy, who opened the Chicago Bauhaus design school in the 1930s, brought with him Henry Holmes Smith and Gyorgy Kepes. Arthur Siegel and Theodore Rozak round out the '30s movement. The show moves into the contemporary arena with the works of Robert Rauschenberg, Adam Fuss, Robert Heinecken, Gilbert and George, Bruce Conner, and Thomas Barrow, among others.
A photogram is made by laying objects on light-sensitive paper in the dark. Then the paper is exposed to a light source and chemically set - just like a photograph.
The photogram, however, can assume quite different qualities, lending itself as it does to more abstract reproduction. As photographic paper became more sophisticated, different kinds of effects became possible. Some of the most complex pieces in the exhibition are color photograms, or collages made on color photograms.
The photogram technique was discovered in the 1830s, when scientists experimented with light-sensitive emulsions, laying leaves and lace on treated paper and exposing that to the sun. But it did not really become an art form until the 20th century when Dada and Surrealism began to surface in Europe.
The artists who worked with photograms in 1919, unknown to each other, were all looking for new modes of expression.
``It was a spontaneous uprising of experimentation and it all happened in the same year, just when Dada was getting on its feet,'' says Nancy Tieken, adjunct curator of the museum's Modern and Contemporary Art department.
The process itself had metaphorical implications that followers of Dada and Surrealism embraced. The form eschews the camera and therefore subverts the photographic tradition - and incidentally, the whole man-centered aesthetic tradition of Western civilization.
The photogram introduced chance operations because results were never entirely predictable. Nineteenth-century science started debates about the dimensions of space, and by the 20th century, had begun to confirm an ``unseen'' dimension to the universe - which undermined the old human-centered, materialist view of the world. Photograms offered a means to express the presence of another dimension.
The positive-negative inversion of light offered another interesting dynamic. The areas of the paper not exposed to light (covered by an object while light is flashed on the sensitive paper) are precisely those that are read as light in the finished photogram, while the paper exposed to light turns dark.
Moholy-Nagy became enamored of light itself, which he thought of as ``energy in motion.'' For Hausmann, the paradox of light-exposures became a metaphor for the unknown - that other dimension that is part of all phenomena, according to the show's catalog.
In their rejection of the old aesthetics, Dadaists and Surrealists studied the flotsam and jetsam of the streets, trash, and objects never before associated with art, says curator Ted Strauss.
Flotsam and jetsam are peculiarly adaptable to the photogram. Then, too, most of the Dadaists were painters who wanted to escape the expressive qualities of the hand, to put some emotional distance between themselves and their work - another emphasis on the almost ``automatic'' photogram process, says Mr. Strauss.
``They were not interested in the world we see because of the huge advances in science,'' says Ms. Tieken.
``They realized the inadequacy of the human eye to encompass what was really going on all around them. There is a strong undertone of philosophy in all this work - a getting beyond the physical world. Moholy-Nagy and Kepes wrote eloquent essays about [light and the photogram],'' she says.
A variety of techniques to ``paint with light'' developed over time, says Strauss. From Hausmann's experiments with sawdust and crude markings - reminiscent both of Edwin Westin's images of sand and of star maps - to Lucas Samaras's ``Skull and Milky Way'' (1966), the metaphors for infinity are many and varied.
Frederick Sommer painted exquisite abstract forms with smoke on glass placed over light-sensitive paper, which was then exposed to light.
Robert Rauschenberg worked with Susan Weil to make photogram images of her. Robert Heinecken placed food on Cibachrome paper and produced images that are both beautiful and slightly horrifying.
Adam Fuss produced one of the most compelling images in the show in ``Language of Echoes'' - a large black and white image of water drops.
He placed the paper in a pan of water and slowly dripped water into the pan, exposing light a little at a time. It has a photographic quality absent in most photograms, yet maintains a lacy, almost surreal quality.
``Many of these [contemporary] artists are pushing the boundaries of what a photogram is,'' says Strauss, just as many of the early photogram artists pushed the boundaries of what constitutes art.