I have a Nikon 80-200 f/2.8 AF-S I'm considering trading for a Nikon 17-55 f/2.8. My lens has a few cosmetic blemishes on the barrel, but perfect optics, the 17-55 is mint. Is this a pretty fair trade? I feel like if mine were mint condition he'd be getting the better deal, but since mine has a few blemishes, it's pretty even. PS yes I know it's a DX lens.. I shoot DX.