Hi, I requested from ILFORD a chart to help with reciprocity failure of ILFORD HP5 Plus sheet film. I got the chart in no time but the longest exposure time was something like 35 seconds. And there it ends. Can anyone who uses Ilford HP5 Plus sheetfilm give me some advice how to properly compensate reciprocity failure when the lightmeter reading is 1, 2, 5, 10 minutes? I have recently started to use my TOYO 4x5 and 8x10 as pinhole cams, so exposeures readings of 5-10 minutes is quite common.