Full frame makes all of the prime lenses more-easily utilized in smaller rooms indoors. On 1.6x Canon, indoors, an 85mm focal length has a very narrow angle of view. On FF, the same 85mm lens becomes more easily used for a variety of compositions...you no longer need to be 35 feet away to shoot a full-length, head-to-toe portrait for an 8x10 crop, but can instead pull off the same shot from 20 feet. With shallower DOF. And, as stated, from 20 feet!!! Indoors, the 24mm becomes a "real" wide-angle. 35mm becomes super-handy for parties and events, and even some portraiture. 50mm becomes a high-speed normal. 24,28,35,50,85,100, 135--all of those prime lenses were developed in the days when people shot pics with small, hand-held cameras on 24x36 size capture medium (aka 'film'). Full frame digital allows the photographer to use these long-established prime lenses in the traditional manner, at normal distances, and inside of real-world apartments, offices, churches, living rooms, back yards, etc..