> Are those 'phantom shadows' due to phosphor_life? Otherwise it is something stupid
> your television does.
No, it is not. But I don't think it is my TV because it does not happen with other shaders, only when I use HLSL with higher shadow mask values applied. Reducing the amount of shadow mask would reduce the phantom shadows but the screen started to look 'fake' and not like a real arcade monitor.
Also, the shadows only occur with specific colors in the background (like light blue or light green). Some examples are the light green seen in the metro stages in Pit-Fighter, or the light blue seen in the Karate Champ intro where the white fighters are jumping away from the bull above the high scores table, things like that.
And when I changed the shader, these shadows are gone. I talked about it with Jezze some time ago, but we couldn't figure out a solution and he said it could be my HDMI cable, since it is way too long. IDK.