The Canonet 28 is a Rangefinder with programmed AE which blocks the shutter release when there is too low light. To override the AE you have to switch to the flash mode which gives you apertures from 2,8-16 at a fixed speed of 1/30.
The rangefinder is good, the release smooth and the film loading support is nice. Put the film in, close the camera, wind three times and you´re on. The feeling of the camera might be the best in the 2,8-lens-class; notice the lever on the aperture ring that lets you switch easy between manual and automatic. The output is enjoyable. Replacing the mercury battery by a 1,5 volt alkaline didn´t make any problems on CN film when setting the ASA-dial 1 stop lower (200ASA film > 100 ASA setting).