RF or RCA Colour Inverter

Hi,

I was wondering if anyone has designed or can design a schematic that will invert (negative style, ie., black is white, white is black) a tv signal.

I dont want to make modifications to the tv/vcr so some kind of external unit that works as an inline device, either inverting the signal before it gets to the tuner, so that I can plug it directly into the tv, or by inverting the signal coming out of the rca video out of the vcr on its way to the tv.

Any help would be greatly appreciated.

Jezza.

If my memory is ok, there was circuit just like that few years ago in Popular Electronics. It was intended to be used for quick preview of
films and dias using standard camcorder and TV.

any ideas what issue or where i can find it?