Well we get these artifacts in shaders with curvature because the aperture mask and/or scanlines are almost but not quite lining up with the pixels of the display. More resolution helps to fix this problem.
When you take a digital photo of a real CRT, the real aperture mask and scanlines are almost but not quite lining up with the sensor in the camera. So the effect is virtually identical to what you see in shaders.
You DO get some of this on real CRTs seen by your eyes and not a camera. But not nearly to the extent that we get it in photos or in CRT shaders.
BTW since I'm posting anyway. I won't have time in the next few days to set up a current build environment and figure out how to do the pull request for crt-geom. Work is beyond crazy and I'm not losing sleep time to this (sorry...). So someone else will have to do it if it needs to be done soon to be in the next MAME release.
I belive u-man posted a compiled version that just drops in over the MAME source with the shader source, chains, effects, and shaders in the right place. I think that cgwg's last update had everything except the compiled shaders. So it should be easy to add if MAME devs want it, right? Just drop the files in and go.
