THE observation of Professor Cheshire and Doctor Curtis that photographic film is subject to a large and, moreover, irregular contraction during the process of development, etc., is confirmed only in the case of non-curling film. For motion picture, aerial, portrait, and process films, the contractions and irregularities are found to be considerably less than in the case of non-curling. In portrait and process film, they are only onetenth of those found by Cheshire and Curtis, averaging but one-twentieth of I per cent. The changes in length and width are not the same, the length of a film showing about 3 ยฐ per cent. increased effect due, probably, to strains in the roll. Film of all kinds is subject to parallel changes in length from day to day and from winter to summer, due to humidity conditions. There is no local distortion in portrait film nor in motion picture or aerial film. Local distortions of IO~ sometimes appear in non-curling film on development, which decrease and gradually disappear in a few days. The factors controlling dimensional changes appear to be humidity, together with the dissolving out in solution as well as the evaporation of low and high boiling solvents in the film base. Important in the secular or contin.uous gradual shrinkage usually found in motion picture film appears to be progressive changes of the film base, the effect of which on dimensional changes depends on the method and conditions of storage.