OK, so what does a professional image editor have to have that GIMP doesn't?

You are incorrect. Each frame of a 24fps film is displayed ("flashed") onto the screen three (3) times. This yields a pulsation rate of 24*3=72Hz. If 24*2=48Hz. were being used
you'd very quickly get a headache.

Thanks.

I found

$ pwgen

to be quite adequate. No parameters required.

Actually PNG screenshots are perfect reproductions of the original screen. There is no blurring at all.