I noticed that when slicing with chitubox or the anycubic slicer, and then printing at the optimum exposure time, that all my prints are exactly 50um (one pixel width) extended in the X and Y direction. This could be due to light spreading beyond the edges of pixels, or due to a calculation error in the slicing software.
Anyway, this results in that horizontal holes are 100um (2 times 50um) smaller in the X and Y direction, and objects are 100um wider than they should be. In the Z direction, all is exactly the correct size.
Regardless of the cause, the solution is simple: Just trim one pixel of all edges in the image layers. I have made a small console app that converts a photon file in order to do this. When I convert a photon file with this app, printed pins exactly fit into printed holes, regardless of print orientation. No sanding required.
While in a Linux command shell, start the program called decreasPixel with two arguments. The first argument is the filename you want to trim the pixels from, the second argument is the filename you want to save the new photon file to. At the moment I only have compiled it for Linux because I don't have/use Windows.