I would not buy filters from anyone who isn't actually manufacturing them. There are a million brands of cheap filters, and God knows who makes them or what quality they are.
Good ones:
Hoya, B+W, Heliopan. Those made by camera manufacturers like Nikon, Canon, and Leica should be good too.
I have bought and used a few of these vintage filters and I have no complaints. I think their quality is as good as the other brands like Tiffen, Hoya, etc. from what I can see.
I would not buy filters from anyone who isn't actually manufacturing them. There are a million brands of cheap filters, and God knows who makes them or what quality they are.
There's more to filter quality than who made the glass. The glass must be perfectly flat on both sides and must be mounted accurately in the filter ring to avoid degrading image quality.
Quite a few aren't coated at all.
I use a lot of uncoated lenses and have found MC filters to be valuable for this application. Since the uncoated front surface of the lens reflects (relatively) a lot of light, it is important that the filter reflect as little of that light as possible.
There's more to filter quality than who made the glass. The glass must be perfectly flat on both sides and must be mounted accurately in the filter ring to avoid degrading image quality.