[Digital BW] Trying to understand ink dilutions on 6-color printers
2003-03-11 by Paul Roark
Dimitri, >I went to the MIS website to check out the ink information... the 4- >ink separation makes complete sense: 25%, 50%, 75%, and 100% Don't take the "dilutions" on the MIS web page literally. They are almost meaningless numbers. The only information they convey is whether the ink is more or less dense than another ink with another number assigned. That is, they indicate the ordering of the densities, but they do not indicate the actual dilution of the black ink or the printed density. >... why is the 4-ink formulation using >25% for the highlights and not something a little off 25%? The 25% is probably closest to the actual reflective density. It's about the same as the Piezo lightest-gray (yellow position) ink. There is no need for anything lighter. The "25%" is already only a few percent black -- very dilute. The "15%" has barely any pigment in it at all. What this tells you is that 6 shades of gray are overkill for a B&W system and the density/dilution curve is very non-linear. It takes huge amounts more pigment to get a slightly blacker black, and a tiny amount of pigment to double the highlight density of an ink. Your are also correct that the human response to the printed shades of gray is logarithmic. >If the response was as linear in the 6-ink as is apparent with the 4- >ink setup, you would get 16 2/3%, 33 1/3%, 50%, 66 2/3%, 83 1/3%, and >100% Actually, you hit close to the relative PiezoBW densities if you scan a test strip and read the scan with the Photoshop eyedropper -- 100%, 83%, 50% and 33% are close to what you'd get. Why there is a larger gap in the middle is unknown to me. >Please don't slam me if the answer is obvious... Not a simple question at all. Paul http://www.PaulRoark.com