Video "quantizing" effect through modulator
Sorry for the strange title but it seemed like a good way to describe the problem I have.
I'm running a Bush TV22 from a PC video source, mixed down to monochrome and fed into an ex-Rediffusion modulator. It looks fine on a test card but actual videos (or images) have annoying highlights. It's particularly noticeable on cloudy sky scenes and faces (see attached). It's as if a slowly rising video level results in a sudden jump in luminance at the CRT (presumably not visible on test card C because only discrete levels are used). I suspect the problem is in the signal generation process rather than the TV. It's not the interference limiter as that is fully backed off and produces a rather different effect anyway. Anyone got any ideas?
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