I want to get some ND filters for my Crown Graphic 4x5. I know that the colour cast of cheap filters doesn't matter for B&W and I wonder how important other factors might be in shooting large format. Would using a set of cheap Chinese filters cause any noticeable degradation on such a large negative? I assume lots of buyers stick these (49mm) filters on 35mm format cameras and find them OK, and I suspect any defects would be far more obvious in that format than in 4x5 - or maybe the defects also get magnified as the size increases, I'm not clear about that.
I'd suggest staying away from them - you're using a good lens and good film so why use poor optics in the chain? I bought one of those chinese cokin-like GND filters - caused a noticeable rainbow like effect, seemingly it acted as a prism of sorts, across the sky. I ended up buying much nicer ones made by a company in the UK.
Hmm. Ok, so what brands are suitable (I'm thinking mainly of solid ND rather than grads ... do square grads even work very well on a lens with a 49mm filter size? An Ysarex 150, as it happens. I've got Lee ND grads but they look ridiculously unworkable next to such a lens).
On a very small lens, if the grad is very soft it might not do much for you. You could use a hard grad then.
I believe Dead Link Removed is the one I have. I have the .9 and .6. From a quick look, they also make hard grad ones. Are you also using yellow/red/green filters or a polarizer? If so, you probably don't need too dark an ND. A 49mm Hoya ND filter from Adorama is only $18 - I think it'll still be much better than the resin ones.
Yes, I've got a huge assortment of old red, yellow, orange and polarising filters (along with soft focus etc) in all sorts of sizes that I picked up for $20 or so , mostly Hoya, Vivitar or Tiffin, but nothing in ND. I guess the previous owner did weddings, events and suchlike, rather than landscapes and other scenes where he wanted motion blur.
I find I often don't need the ND for B&W. A polarizer is good for 2-3 stops, and a red or yellow another 2. Of course, I often shoot very slow film (or paper - ASA 3) which helps. If you're already using other filters, you might want to stick with a thread on filter rather than the square ones - I find it awkward to use both. Also, the square holder doesn't allow the use of a hood (could be argued that it's a hood of sorts but I don't think so).
A strip of developed 120 film could be they cheapest diy ND filter option. It fits a 52mm filter with room to spare on the sides. If you can stretch it taught over a filter, or cut it precisely and drop it into a UV filter, it would work fine. Double layer it for a darker ND effect.
A cheap (and good) way would be to get an old adapter ring for Series filters. You can find Series filters for close to nothing, and IME they are very well-built filters that should still work today. Series VI will cover many press camera lenses, and will also give you the widest selection of filters on the used market.
I've gone with Hoya. As well as the 48mm-thread Ysarex I've got a Xenar with a Series VI holder, so I'll keep an eye out for filters to fit that and I could experiment with exposed film (but I guess the filter factor would be quite variable for that).