Investigation of your pp3 file shows three things:
- You have automatic CA correction enabled. Is that really what you want if you’re interested in the camera SNR?
- You use a LCP file and correct for geometry and vignetting. The geometry in particular can distort pixel values (maybe unnoticeable by eye, but maybe visible when doing calculations).
- You have resize enabled? Why?
Taking there three things into account, I’m even surprised the curves are not deviating more than they are…