I have a 85mm f1.2L II which I bought two months ago. I found a lot dusts on rear element and I couldn't blow off them. I don't want to to touch the glass by myself. Question is: can I mail the lens back to Canon to have lens clean for free? How? thanks
As Beauchamp says, you shouldn't really have a problem with gentle cleaning.
If you bought it new, it is under warranty, and of course Canon will clean for you. Just box up and ship to a Canon repair center with a copy of your invoice.
Otherwise, the focus is okay, not out of adjustment (front or back-focus?). You should fully check it out so any other issues can be addressed a the same time.
The 85 f/1.2 is rather famous for getting dust under the rear element. I don't know how it gets there, but it does. Really nothing to worry about, it's inevitable.
But if you are really OCD you can take out the 4 mount screws, lift the mount just a bit from the side opposite the electrodes (not too much, there's a flex cable connecting the electrodes to the len's electronics) and use a rocket blower to blow it out.
