Roger Cole
Member
Regarding those colour filters - can I use those as black and white multi grade filters too?
You CAN, and it will work, but I'd recommend a separate set of MC filters. Becuase:
You can use the magenta and yellow filters to control contrast with multigrade papers. The magenta filters block green and pass blue, while the yellow filters block blue and pass green. The red passed by each is not a factor. You control contrast by exposing with different combinations.
This is exactly how it works. But the difference, besides convenient markings in contrast grades instead of having to consult a table for relative filtration values (with a little practice you get a feel for this though) is that the MC filters are speed matched. Such matching is only approximate in the sense that due to the very nature of contrast changes they can only be matched for one chosen gray value. But that's usually a pretty useful middle gray level and in practice you can swap filters and change contrast, use the same exposure (or a stop more if you go from anything 00 - 3.5 up to 4 - 5 which are half the speed of the lower filters) and get a print that looks very similar except for different contrast. You can vary exposure a bit from there. In other words speed matching isn't perfect or essential, but I do find it handy.
That said lots of people use a dichro color head to print black and white giving them the ability to dial in filtration for VC combined with the benefits of diffusion. That's probably a worthwhile trade-off for loss of the mid gray speed matching.