Jaws
gDocCross Modulated Screening is a hybrid approach to screening, aiming to take advantage of the best features of both AM and FM techniques.
AM screens at high frequency can produce excellent reproduction in the mid-tones, without the slightly grainy effect in flat tints that FM screens sometimes introduce. But they can lose detail in the highlights and shadows as very small dots are lost during imaging.
FM screens hold shadow and highlight detail well, because the dot size can be tuned to the device and media; they are simply moved further apart for the extreme highlights and shadows instead of being reduced too far to be retained reliably as they would be with a high-frequency AM screen.
The intention with cross-modulated screening is to limit the smallest structure produced to be that which can reliably be printed on the target system. Once this point is reached, within a given hybrid screen, structures are removed completely rather than continuing to be reduced in size to create the required tonal range.
A cross-modulated screen therefore switches from an FM-like pattern in the highlights to an AM-like pattern in the mid-tones, and back to an FM-like pattern in the shadows. This has the effect of being able to print screens at a higher line ruling than would normally be considered reliable on a given system, without losing highlight or shadow detail.
