[SOLD]: 10-22mm & 30mm APS-C lenses

[neuroanatomist]

I like the idea of a variable ND filter. However, a couple of things have prevented me from buying one. The first is the IQ issue Sean mentions with the less expensive Genus, leaving the Singh-Ray as the only convenient option - or so I thought.

Note that I'm ruling out the Schneider version, which is a pair of rectangular filters in a rotating holder - incidentally, iND, that directly answers your question about stacking polarizers to mane a variable ND. The product description states: "The kit is comprised of a screw-on 77mm True-Match Circular Polarizer (Non-Rotating) that mounts to the front of the camera lens, a 4x4 True-Match Linear Polarizer that slides into the Schneider 4" rotating Filter Holder with the 77mm W/A adapter ring." As it turns out, searching for that product description led me to the discovery that Schneider now makes a threaded variable ND filter, too, claiming 1.33 to 11 stops. It's non-vignetting since it uses their extra wide design (the glass is ~95mm while the threads are 77mm). I just wish there was an 82mm version...

Anyway, the other reason is that 'banding' that's mentioned in the Cons link form iND - the blog author doesn't state this, but I expect that he saw that using a wide angle lens. Since a vari ND is crossed polarizers, it's subject to the same uneven polarization you get with a CPL on an ultrawide (<24mm FF) lens, which manifests as a Maltese cross effect that is worse at darker settings. My primary use for the dark end would be on wider lenses.

I may still try a variable ND at some point, but for now I'm happy with the standard ND filters - I use a 3-stop filter for shooting fast primes wide open in daylight, and for mild blur on moving water, and a 10-stop filter for extreme blur on moving water and for blurring people out of architectural shots.

[iND]

Thanks Everyone for this discussion.
It has been exceptionally helpful.

[Sean Setters]

If I don't have any takers on the lenses soon, I'll be posting them on Ebay--just a head's up.

[TimT]

I have a 30mm Sigma and I love it, especially for low light indoor shots.