I recently bought the 24-105mm F/4L lens for my 50D and have a few newbie question about it. I want to keep a filter on it for a "peace of mind". 1. Do most filters allow the lens cap to work properly? 2. Do filters interfere with the OEM lens hood? 3. Clear glass or UV? (only concerned about protection) 4. In low-light, can UV affect shutter speed at all? 5. What is the best filter for around $50? Thanks in advance!