I own the Canon EF-S 10-22mm f/3.5-4.5 and I love it. The view @
10mm is phenomenal! On your 50D set the aperture to f/8 and the
Hyperfocaldistance will be 2.19ft. If you focus on anything
reasonably close to you and then recompose almost everything in the
frame will be sharp. Heck, even at f/3.5 the Hyperfocaldistance will
be just over 5 ft! The FoV and DoF are HUGE with this lens.


All of these calculations were done using DOFMaster with a Circleofconfusion of
0.019 mm. I am not sure if that Circleofconfusion is optimized for the 50D but it should be a good starting point.