I have a 17-55 IS with a third party lens hood. Nice hood, sturdy, flocked, etc. Sometimes when shooting the lens hood rotates and if I don't catch it I get part of the hood in the image (corners). I'm not sure if it's the hood or the lens causing the problem. It may be that I need a Canon hood, and if so I'm fine with buying one. I just thought I'd throw it out here first and see if a) These lenses are known for loose hood issues b) There is a way to fix a loose hood c) a Canon hood will definitely solve my issue (before I spend the money to find out it doesn't).
Chris
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