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 Photoshop. I'd be happy to have a way to create a preset in the text file or something if that is possible as the curve would be the same for all images made into negatives and darkroom printed to the same medium.