He is regarded as one of the founders of the international photo-realist movement of the late 1960s, with such painters as John Baeder, Chuck Close, Robert Cottingham, Audrey Flack, Ralph Goings, and Duane Hanson.

Author Graham Thompson writes "One demonstration of the way photography became assimilated into the art world is the success of photorealist painting in the late 1960s and early 1970s.

He frequently studied the works of realist painters such as Edgar Degas, Edward Hopper, and Thomas Eakins, who are strongly represented in the Art Institute's collection.

"[2] Estes stayed true to the photographs he used: when his paintings include stickers, signs, and window displays, they are always depicted backwards because of the reflection.

The paintings were based on Estes' color photographs, which captured the evanescence of the reflections, changing with the lighting and the time of day.

His paintings provided fine details that were invisible to the naked eye, and gave "depth and intensity of vision that only artistic transformation can achieve.