Wellington was sent to New York to work under George Eastman in 1890, returning to England to become the manager of the new Kodak Works in Harrow (1891-93). He later worked for Elliot & Sons, Barnet, then founded Wellington & Ward in Elstreet with his brother-in-law H. H. Ward, serving as scientific and technical director. The firm later merged with Ilford Ltd. Among other innovations, he developed the Iso-Wellington photographic plate (a fast, finegrain emulsion) and the Silver Intensifier (1889), which helped control density. He further improved upon his own formula in 1911 by inventing a process that did not stain or dissolve the emulsion of some plates as the original had.
Though his major contributions to photography were in the laboratory, Wellington was an accomplished pictorial photographer as well, depicting genre scenes of the Edwardian leisure class.
A member of The Linked Ring, Wellington joined RPS in 1887 and was elected an Honorary Fellow in 1935.