The lens block moves when focusing - I'm afraid it won't suck dust. The lens hood is needed only when the filter is screwed on - the front lens is recessed into the body in order. If your carcass does not have AF adjustment, check for back and front focus when buying. Larger than 50 / 1.4D and filters for 52 will not work. After / 1.4D, there are many times fewer autofocus misses, there are almost no marriages from the session rushing around like mad children.