I just purchased an S5-IS and have been comparing its performance with the S2-IS I have been using. While the S5's viewfinder image is markedly brighter than the S2's, some scenes that are quite clear in the S2 are not in the S5. Specifically, a dark log in a very mild fog was nearly invisible in the S5 viewfinder, but clearly visible in the S2. As a consequence, I had trouble composing the shot in the S5. (The brightness of the S5 viewfinder is set at the lower level.)
Has anyone else encountered this problem? Is it a bona fide difference between the S5 and the S2? If so, is it considered a feature or a design flaw? Is there any fix for it? Canon support wants me to send the camera in for service, though I've had it less than a week. The viewfinder seems fine under more normal conditions, so I doubt that it is a serviceable defect.