I'm pretty heavily invested in 77mm filters, because my Tokina was my widest thread at 77mm. I use step-up adapter rings to use them on my other lenses that range from 49mm to 67mm, and that works okay as long as I keep those filters clean and well out of focal range. (I have a CPL and an assortment of NDs, and use them for landscape photography only.) I've just upgraded from a 60D to a 6D and needed to replace that equally terrible yet versatile 18-135mm EF-S kit lens. Of course, all the standard zooms for FF are threaded for 82mm filters. I went with the Sigma 24-105mm art, which won't be arriving for about a week, so no, I can't do tests with it because I don't have the lens in hand and I don't have (not yet, anyway) an 82mm-77mm step-down ring...
I've read all the other topics I could find on the subject, and sure, yeah, of course I'll get vignetting if I put the 77mm ND on the 82mm Sigma -- and it'll be worse at wider angles. I wouldn't be surprised if I got much worse than a bit of vignetting, like total darkness, leprechauns or any such thing at the periphery. I get that. So here's my question:
Is the *amount* of peripheral damage I'd experience using a 77mm filter with a step-down ring on the 82mm Sigma be "small" enough such that I could compensate for it by shooting a little wider and simply cropping in post? Or if shooting any wider simply widens the problematic part of my image, then I'm just stuck with the crop in post to remove the ugly bits?
If any of you gear heads have an example image that you could post here using any stepped-down 77mm filter on any of the 82mm dia. FF standard zooms (24-70mm, 24-105mm), shot at 24mm, that would be very interesting to see. Obviously, I'm struggling with the idea of whether to buy an inexpensive step-down ring or invest a lot of money on all new filters -- especially now that my standard zoom, which used to be my softest lens, will soon be the sharpest lens in my bag. Note: My wife, who likes my photos just fine already, is less than pleased about the cost of the FF upgrade. Adding filters to the damage done could prove problematic. A common problem with photography, in my experience...