Determining reciprocity failure experimentally?
I've been thinking about doing this for the x-ray film I'm using. Is there any standard procedure for this? I was thinking of taking a bunch of gradated exposures in a low-light setting. Against what frame of reference would I compare the results, though? This is the part I'm not clear on, given that there's no easy way outside of using a densitometer and the spec sheet, the former of which I don't possess.
Re: Determining reciprocity failure experimentally?
easy way - https://www.photrio.com/forum/thread...-effect.62519/. You could probably reach out to Andrew for his advice.
DIY Way
use a step wedge in front of your 4x5 film, Take several shots at different f-stops keeping time same, measure densities and see how far off a certain tone drifts. IF linear it will change 1 stop, but probably not and your plot will show it to you. You could also do it under an enlarger as a contact stepwedge to film print, raising the light and using neutral density filters for longer exposure times. Proccess all your film together so there is no variance in development.