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Though there was a time when presenters knew not to wear anything with narrow vertical or fine chequerboard patterns, because the resulting high-frequency luminance signal would bleed through into the colour signal causing phantom colour effects. Interestingly the effect occasionaly occurs today, here in the UK where people use old Sky boxes to provide an RF output to a TV in another room.



Wasn't that long ago - it changed fashion - all those hounds-tooth jackets, paisley ties etc etc stopped being seen in public (on TV) and were replaced by solid colors.


Do you mean like when a moire pattern may sometimes appear to have a ghostly coloured after-image? I've seen this in old black-and-white films shown on colour TV. I've been trying to describe that to people to learn more about what it is but I always fail to. I feared there might be something wrong with my eyes. Is there a name for this effect?


For Tv's the colour is caused because the colour signal is hidden as a high frequecy component that older B&W Tv's would ignore. Conversely, a high frequency signal caused by closely spaced light and dark patterns fools colour TV's into thinking there's a colour signal present (as the filters in TV's improved the magnitude of the effect reduced, but it's there to this day in analogue TV).

What you're seeing is probably Fechner Color [0]. I've seen the effect myself, as I recall there was a bit of a craze for demoing it some years back.

[0] https://en.wikipedia.org/wiki/Fechner_color


Thanks. It could well be Fechner Colour.


Back in the 1980s, D-MAC was touted as the system that was going to eliminate that problem. Separation of analogue chrominance and luminance was specifically called out as a feature in popular science explanations.




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