Exposure times for paper as film with filter

I have just recently found an interest in pinhole photography and feel very enthusiastic about the whole thing.
So far I have just taken about a dozen pictures, all on Ilford Multigrade IV RC. The first ones without filter, and the rest with. In most cases the exposure times, based on estimations made by myself and others, have been far from accurate.

When enlarging using the same paper I do not prolong the exposure times when using the filters but for those of the highest numbers. Since I have not used any of the high numbered filters with my pinhole camera the exposure times have consquently not been prolonged because of the filter used (but the reprocity factor has been taken into account).
 
When looking into Ilford's fact sheets for Multigrade paper I find that they state the ANSI Paper Speed to be 500 for unfiltered paper, but when using their Multigrade Filters 00 - 3-3 1/2 the speed is stated to be 200, and for filters 3 1/2/-4 - 4 1/2-5 the speed is 100. Does this mean that I shall calculate with ISO 6,67 * 200:500 = ISO 2,67 respectively of ISO 6,67 * 100:500 = ISO 1,33, since I have learnt that this Multigrade Paper without filter has ISO 6,67?

I have also learnt that some recommendthe softer versions of fixed gradation papers. Is that something that can be generally advised instead of Multigrade, and if so - why?

And finally, does the Ilford Multigrade IV RC has a tone of filter #2?

Dennis Johanson
Received on Tue Jul 10 03:13:48 2001