Color Management Part 1

The densitometer has three filters (RGB), each of which can isolate roughly a third of the visible spectrum. Measuring the reflectance values through each of the red, green, and blue filters tells us the ink film densities for the cyan, magenta, and yellow, respectively. It tells us the "amount" of ink (or pigment) we have on the press sheet—which is what the pressman can directly control at that point. But it doesn't specify what color the ink is. In fact, we could take readings from two dark reds that were clearly different colors, but they could conceivably have the same density reading. Invaluable as the densitometer is press-side, it doesn't tell us what we need to know to build that 3D map.