Continued...
The closest to a "100% pure video signal" from an LD that I think we'll ever get is a TooT of 3 captures from 3 different copies of the same movie on LD (pressed by the same pressing factory, preferably) on an LD player with a >51dB signal-to-noise ratio that doesn't smear CLV LDs (if the LD in question is CLV, that is).
What a mouthful!