Question: Do you use UV filters on your lens?
If you cant see any negative optical effect on your images using a UV filter then using a UV filter is a good idea.
I found a UV filter effected my long zoom 150-500 and some smaller primes.
That said.......
I bought 2 x 77mm B+W limited edition Gold MRC UV filters, i got them for $70 AUD each, NEW from a wholesale dealer importer, lovely box and presentation.
The A B and Blind Test...............
Ok on my 24-70 2.8 G and D3X in sunlight shooting a brick wall building and roof with a blue sky above, the difference was measurable/noticeable but small.
With the filter on it added a tiny little micro colour contrast, it was like using a very sublet gentle polarizer to describe the difference, it of course not a polarizer.
The mortar between the bricks when zoomed in seemed to have nicer more natural colour and contrast detail, is that possible ?, well its the only way i could describe it.
As to the A B comparison of images side by side standing back looking at them on a 30 inch screen, the filter on was ever so slightly noticeable and the preferred look even in the blind test.
So many people say they cant see the difference or benefit and that seems often to be the case, well i feel the variable in all that is the glass, camera, graphics card, and screen they use as well as the type of filter in question.
My self, i give it a tick and use only this particular B+W limited edition Gold MRC UV filter for positive optical benefits outdoors.
ie: if its adding and not taking away anything its a win.
Only an opinion