AFAIK, preventing vignetting is the only advantage to a thinner mount. Whether or not that benefits a particular lens/filter combination will depend on the lens and the filter. B+W F-Pro mounts are a bit thinner than many other mounts. Since you have a few 77mm filters already, you can see if the Singh-Rays will vignette by stacking filters on your existing lens. The F-Pro mount is 5 mm thick (as is the B+W Slim CPL; the standard CPL is 8 mm). Singh-Rays mount thicknesses are listed here. So, for example if you're considering a Vari-ND, stack 3 F-Pro filters for 15mm thickness, and if that doesn't vignette on the lens(es) that you'll use it with, you're fine. If it does vignette, but a stack of 2 F-Pro filters doesn't, you'll want the thin mount Vari-ND. As I tested previously, even the UWA 10-22mm doesn't require a B+W Slim or XS-Pro mount, although the standard mount Vari-ND would vignette on that lens.
If the glass is thinner too (as is the case for some of the Hoya filter lines), that might confer an optical advantage, on the basis that less glass will result in less aberrations. But that only holds true if the thinner glass can be made to the same tolerances, and the thinner the glass, the more difficult it is to get it perfectly flat.
Hope that helps...
John
Originally Posted by barba
Check out the XS-Pro mount from B+W. It's just a little thicker than the Slim mount (3.4mm vs. 3 mm), and it has front threads so the standard cap works.
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