I post too Much on Here!!
- Jul 21, 2010
Of course. The back of the lens is open, so air (and dust, OMG!) get in. Zooming and focusing move element groups within the lens, and that moves around the air (and dust, OMG!) inside the lens.My 70-200mm f/2.8L IS II USM, may it rest in peace, had dust between the front element and the one behind it, though it doesn't extend.
Some people seem to think non-extending zooms are hermetically sealed. Lol.