I'm trying to use Affinity Photo to make a curves adjustment layer for digital negatives that will be used in a traditional darkroom process. I need to be able to compensate for the response curves of the medium (e.g. photographic paper, cyanotype) I will be contact printing the negative to. I can calculate the curve but I can't find a way of telling Affinity Photo to make an adjustment curve where input value 5 maps to output value 20, input value 16 maps to output 32, etc. as is possible in Ph