The QL17, QL19 and QL25 are all essentially the same, differentiated only by their f/1.7, f/1.9 and f/2.5 45mm lenses. This was very much the mainstream of cameras in the ’60s.
The AE-1 marked the introduction of micro-processor electronics to photography. For the first time microprocessors calculated exposure and timed the shutter, which in this case was still a fairly traditional horizontal cloth design.
The Canon A-1 was the first camera to offer micro-processor controlled, programmed auto-exposure, where both aperture and shutter were determined by the camera.
A groundbreaking design departure for Canon, and one which established the pattern for almost every DSLR they sell today.