Another way to step up the resolution a notch is using photoresist coated PCB and a small UV laser. It is typically a negative process (exposed photoresist diss

Another way to step up the resolution a notch is using photoresist coated PCB and a small UV laser. It is typically a negative process (exposed photoresist dissolves in developer solution), so you'd have to invert your plot/gcode, there are two extra steps (developing the exposed photoresist so it dissolves and dissolving the remaining photoresist after etching in acetone bath). However, that brings you closer to being able to prototype a PCB for something with 0.5mm pitch.