I own a Nikon 20mm f/2.8D lens but would like to get something a little wider; however, the 14-24mm f/2.8 is more than I'd like to spend. My local camera store said the Nikon 16-35mm f/4 would be a good alternative optically so if I decide to sell my 20mm, do you think the 16-35mm would be a comparable quality replacement? There don't seem to be many ultra wide angle lenses available that offer decent quality photos. It is for use on a D600. Thanks for any ideas!