Dngallagher wrote:
Are you using a UV or skylight filter on the 300? An inexpensive filter can cause all sorts of trouble, in fact it is my belief that ANY filter will degrade performance of other wise good lenses in odd ways. I pulled all of my UV filters from my lenses recently and image quality improved dramatically for me across the board.
Thanks for the brainstorm. I use no filter at all, counting on the lens hood to protect the glass. Hasn't failed me yet.