I know Affinity Photo is a raster program and can only select whole pixels but never had this problem with PS.
I shift drag out an elliptical marquee tool circle and end up with something pretty rough looking with some odd flat edges, this is even more apparent when I outline the selection. I'm working on both 300dpi & 72dpi documents and it makes no difference, I have antialias checked, not sure what else to try.
I've got to produce pixel-perfect artwork for cinema posters so can't have jaggedy bits.
Any help appreciated