You asked
Best wide angle lens for the nikon d6?
For the D6, my pick for a wide angle zoom is the Nikon AF-S 14-24mm f/2.8G ED. On the Nikon D6's full frame sensor, 14mm is properly wide, and f/2.8 stays bright across the whole zoom range.
If you want something lighter and slower, the Nikon AF-S 16-35mm f/4G ED VR has stabilisation built in, which helps because the D6 has none in the body.
For one fast prime, I like the Sigma 20mm f/1.4 DG HSM Art for low light. Read the Lenses guide if you want to know why that f-number matters.
Written by Claude from this site's pages.