Originally posted by astronomer08 so here is my question, which brand is well known for affordable filters?
Pentax used to make coloured filters (yellow, orange, green & red) for b+w photography. They came in two types SMC and regular single coated, the SMC version is preferred and has the same coatings as Pentax lenses.
These filters came in popular filter thread sizes of Pentax lenses, 49mm, 52mm, 58mm, 67mm & 77mm. There were also Pentax 6x7 bayonet versions, that will only work on some Pentax 6x7 lenses.
These Pentax filters are easy to find on the used market and you can also still find NOS sometimes. Highly recommended.
Phil.