When printing colors other than CMYK, many users understandably turn to colorimetric information (CIE LAB, Delta-E). Frequently overlooked, however, is the importance of using optimized density metrics for process control in the offset lithographic pressroom.  One such metric, available on many spectrodensitometers, is spectral density (sometimes called “density-by-wavelength” or “lambda density”). A brief illustration of how a densitometer “sees” color ensues, followed by an overview of spectral density. Consider looking at a printed cyan ink…