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Need your expert and sage advice again. I have a Schneider Symmar-s 6.8 360mm, a Rodenstock Sironar-N5.6 240mm and a GoerzDagor 6.8 9 1/2" lens. I can't figure out what mm filters they take. If you have one and can pass on this info I would be gratefull. Also, What are you'll doing for filters on LF lens? Do you get the filter to fit each lens or some other type of method. Like Cokin or something.
Thanks again for what expect to be great insight into this seemingly simple task.
When you have such a mismatched bag of old and new/big and small glass, it might be a whole lot easier to look at a Lee Fliter system versus attempting to carry potentially three sets of screw in filters or pay to have adapters machined. The Lee will cover just about any filter application with a singular set of fliters and do it at a pleasing price. They have a web site. Cheers!
From manufacturer's product literature that I have, the 240 f5.6 Sironar-N takes 77 x 0.75 mm filters and the 360 f6.8 Symmar-S 120 x 1 mm filters. I have listed thread diameter and thread pitch -- the later will probably be correct on any filter of the correct diameter. You can check that your lenses match these values with a ruler -- layer a metric ruler across the diameter should give a reading slightly less than the numbers above -- threads are defined by the outside diameter of the male thread, not the inside diameter of the female thread.
An older lens like the Goerz Dagor might not have threads intended for filters.
A 120 mm diameter filter will be a special order item, if even a special order is possible. It will cost a lot of money.
I use round glass threaded filters and step-down rings to adapt to various lenses. With your Dagor and the huge filter size of the 360 mm Symmar-S, this method wouldn't work very well for you. Probably best would be some filter system, or taping gelatin or thin polyester filters to the front or to the back of the lens. It is optically sub-optimum to use thick filters on the rear of a lens. If you still decide to use a thick filter on the rear of a lens, focus with the filter in place.
By far the largest of the three lenses is the 360mm Symmar-S lens. One might also refer to it as the Suma-S lens. It's huge, with a filter size of 120mm. I had one that I sold recently.
The usual strategy is to purchase filters for the largest lens, and then get adaptors. But, I'm not sure that anyone makes a 120mm filter. Schneider makes a 122mm, but I don't see a 120mm. At any rate, your best and least expensive strategy is to rear mount filters for your lenses. You can get a Xenophon 4" rear filter holder for each lens board from Calumet. Then, drop in 4" gelatin filters when you need them. If you use a reduction lens board, then you might get away with using only one Xenophon on the reducing lensboard.
Some will complain that rear mounted filters will throw off the optics. While there can be an additional problem for very short focal length lenses (your's aren't), the only possible issue for your lenses is that it throws the focus off by about 1/3rd the thickenss of the filter. This is negligible for gels and can be corrected by focusing with the filter in place. In fact, I was told by a Schneider LF Tech that rear vs. front mounted filters can reduce flare.
I use the Lee System. A bit expensive but it works great.
Jeff
I use the Lee snap on system with the 4" polyester filters. Cheap & effective. The filters are kind of hard to keep clean without scratching, but the system works very well.