I own a Canon EF-S 17-55mm f/2.8 IS USM Lens. The other day I was trying to take a photo with the camera pointed directly towards the ground and mounted on a tripod. When I let go of the lens after adjusting the zoom, it would fully extend on its own due to gravity.
I am not certain if it has just now started doing this or if it has always done it and I haven't noticed because I am normally holding the lens while shooting. Is this normal behavior for this lens? If not is there an adjustment I can make to eliminate this behavior?