a film cassette is disclosed wherein a pair of annular constraining flanges are coaxially spaced on a film spool . the flanges radially confine the outermost convolution of a film roll wound on the spool to prevent the film roll from clock - springing against the cassette shell and thereby hindering film movement . a pair of internal cam members are rotatable from outside of the cassette shell to open a light lock by slightly separating opposite throat portions of the shell . another pair of internal cam members are rotated with the first pair to flex a limited section of the flanges apart an axial distance sufficient to radially free a corresponding section of the outermost convolution . then , rotation of the film spool will cause successive sections of the flanges to be momentarily flexed apart , and each freed section of the outermost convolution will be advanced automatically to the outside of the cassette shell .