Between 1922 and 1935,
Alfred Stieglitz made more than 200 photographs that he called Equivalents. He wrote to a poet friend,
Hart Crane, about them that “there is more of the really abstract in some
‘representation’ than in most of the dead representations of the so-called
abstract so fashionable now.” Closely cropped views of clouds, generally
without a horizon line or any other landscape features or buildings to serve as
reference points, verged on the nonrepresentational. These photographs were
among the first that directly abstracted recognizable—albeit intangible—content
to create images in which a viewer could construct any number of symbols or
interpretations.

In
his own words, Stieglitz turned his lens skyward “to show that my photographs
were not due to subject matter—not to special trees, or faces, or interiors, to
special privileges, clouds were there for everyone—no tax as yet on them—free.”
His theory of equivalence, where a photograph could evoke something beyond its
actual subject, was hugely influential for generations pursuing abstraction.