Eugene was uniquely labeled in 1889 by art critic Sadakichi Hartmann the “painter-photographer.” What made Eugene so attractive not only to his contemporaries but also to Stieglitz was his totally unorthodox method of rubbing oil onto the negatives and adding cross hatching with an etching needle sometimes leaving only small portions of a picture recognizably photographic. Charles Caffin, who’s landmark book Photography as a Fine Art (1901), saw in Eugene and argued that only a trained and gifted photographer was in the position to create such delicate images and alter their power of expression so masterfully by manipulating them. He attributes a very special quality to the photograph The Horse characterizing it as… Eugene’s quintessential landmark image. 
Eugene’s technique of scratching the negative struck a nerve in the ‘photography as art’ movement amplifying the ongoing debate over whether manipulating a photograph to make it artful is acceptable in the ‘photography as art’ arena. “It has often been said that the photograph was reminiscent of an etching. But that was in no way intended. The banal surroundings which were inessential and disruptive to the photograph as a whole were removed from the negative with a retouching knife, but nothing else was changed, neither the light nor the shadows, nor the form and line of the animal’s body.” Or more succinctly “The aim is to express the inessential in favor of the essential” 
Very little of Eugene’s work survives today – a typical fate of much that has to do with the history of photography and an indication of how little is known about the medium and how low esteem that part of our cultural heritage is held.
Frank, Waldo D. America and Alfred Stieglitz: A Collective Portrait. New York: Aperture, 1979. pl. 3
Frizot, Michael. New History of Photography. Place of publication not identified: Pajerski, 1999. Print p. 297
Harker, Margaret F. The Linked Ring: The Secession Movement in Photography in Britain, 1892-1910. London: Heinemann, 1979. pl 3.14
Kruse, Margret. Kunstphotographie Um 1900: D. Sammlung Ernst Juhl; Hamburg: Museum für Kunst u. Gewerbe, 1989 pl. 857
Roberts, Pam. Photohistorica: Landmarks in Photography : Rare Images from the Collection of the Royal Photographic Society. New York: Artisan, 2000. p. 199
Taylor, John. Pictorial Photography in Britain, 1900-1920. Cambridge, England: Chadwyck-Healey, 1900. (plate 20).
 Naef, Weston J. The Collection of Alfred Stieglitz: Fifty Pioneers of Modern Photography. New York: Viking Press, 1978. p. 96
 Eugene, Frank, and Ulrich Pohlmann. Frank Eugene, the Dream of Beauty. Munich: Nazraeli Press, 1995 p. 241