I’m no expert in the slightest, just having some fun in affinity photo since I’m waiting for a friend to come over. Looks to me like the negative/inverted image slipped slightly to the right and now the light spots get darker and the dark spots get lighter.
I didn’t have any photos with dark backgrounds and a relatively high contrast at hand. I took these courtesy of Cats and Dogs.
Photo shenanigans
Both images are made from one original layer and an inverted top layer, blended with the normal blend mode, slightly lowered opacity for the top layer and adjusted ranges for the blending.
Not perfect but maybe a step in the right direction!