I'm not a Canon user, but a shutter of 1/50 is perhaps a little slow for an EFL of 80mm (assuming you used that 50mm prime). I would try again in better light with shutter priority set to 100 and see if that improves sharpness.
Also, in challenging light, I sometimes find burst mode helps. If you shoot 3 images in burst, then the 2nd one isn't influenced by you pressing the shutter button.
Another option would be to try again with a tripod to rule out focusing problems (by you or the camera).
I'm having similar problems with soft images, but increasing the shutter speed or using a tripod doesn't seem to help me much - maybe it could help you though.
I started a thread regarding similar issues to yours: http://www.cameralabs.com/forum/viewtopic.php?t=18868
Panasonic G3: 9-18mm, 14mm, 20mm, 45mm