The datasheet cites a speed of ISO P500, which is clearly a different ISO standard from that of film. I have it in the back of my mind that it's something like ISO 4-6, but I wonder if anyone can confirm this. I plan to use some Multigrade paper in a pinhole camera, though the camera instructions (it's the Ilford Obscura) don't give any guidance on this. It'd also be good if anyone can give me advice on how to approach the problem of reciprocity failure with such paper. Many thanks.