A composite video signal has both the colour and luminance in the same ‘space’. The colour is modulated on a ‘subcarrier’ frequency (CSC) which is filtered from the luminance in the display, but in certain situations it can remain as a pattern of dots and is known a ‘Cross Luminance’. In a similar vein, any frequency information in the luminance signal that happens to be near the CSC can be mistaken for colour and give ‘Cross Colour’ effects. These are typically shimmering rainbow type patterns on patterned subjects like tweed jackets. These effects could be made worse by the detail enhancement circuits that add high frequency components.
Some cameras have a menu function to help called ‘Cross Color Suppression’: Separating the luminance and chrominance components of a composite signal can be a difficult task, even with the most advanced comb-filtering techniques. In order to keep cross colour and cross luminance to a minimum, the Suppression function effectively eliminates frequency components that may result in such artifacts being generated prior to the signal output. These frequency components are virtually eliminated from the Y/R-Y/B-Y signals within the camera head through sophisticated digital three-line (NTSC)/five-line (PAL) comb filtering, resulting in a great reduction of the cross color and dot crawl normally seen on picture monitors fed with a composite video signal.