Hi!
I just got my new Canon EF-S 55-250mm IS lens. I have two problems with it:
1) Sometimes focusing leads to slight shift in the inner elements of the lens. That translates into blurry images if you make a shot right after focusing. If you focus once again, the problem seems to not be present anymore. (Strangely this does not happen when using Servo focusing) edit: this only occurs when IS is switched on, so it's probably the culprit
2) I can hear an alarmingly loud buzzing sound when using a relatively low shutter speeds (less than 1/20) while IS is off. The sound disappears if I point the camera straight down. edit2: This also makes picture look blurry
I know this is a cheap lens and one can't expect too much, but I am really disappointed. Does anybody have similar problems?
Thanks 

