Reciprocity for paper??

Is there a reciprocity failure consideration for Ilford Multigrade as a paper negative when used for long exposures of, say, 15 minutes or so.

Just from experience, not from careful measurements, I don't think there is much reciprocity failure. I've had some 2 or 3 hour exposures come out less exposed than I expected, but in that amount of time light changes. I think up to an hour or so you're safe, and longer than that might need some correction.

ColinRH said:

Is there a reciprocity failure consideration for Ilford Multigrade as a paper negative when used for long exposures of, say, 15 minutes or so.

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Yes, there is some low-intensityRF with paper even when enlarging but it differs so much from paper to paper thatonly a test will tell. I add50% from measured for my pinhole paper negatives.