John, You are at the same point as I am. Well, actually I'm a little ahead. The density readings are log to the base 10 so dividing the Dmax by 2 will not give you the expected 50% reading. I am currently trying to figure out the math. I will let you know when I get there, Barry --- In DigitalBlackandWhiteThePrint@y..., John Chervinsky <chervinsky@d...> wrote: > Hi, > > I am attempting to calibrate my printer output using a calibrated X-Rite 810 densitometer. I am using MIS FS inks through an Epson 1160 onto PhotoRag 308 paper; I am on a Mac computer. I realize that this question has come up in the past, but practical elements of technique were omitted. Below you will find the reflective densitometer (visual) output vs a 21 step stepwedge. I did measurements using both the Randall and Piezography workflows. If you look at the numbers carefully, you will conclude as to how shockingly non-linear they are. I would have expected, for example that the 50 % reading would have been close to 1.7/2 = .85. The Measured value of around 0.6 is WAY off! > > Has anyone else had this experience? I would not think that my paper choice would have that much effect. Are there subtle differences in using a reflective densitometer as opposed to a spectrophotometer to do the measurements? It would seem that for grayscale work that a densitometer should be fine. Please advise. > > Thanks! > > -John Chervinsky > > > > STEPWEDGE CONE RANDALL > 100.0 1.71 1.77 > 95.00 1.54 1.66 > 90.00 1.40 1.57 > 85.00 1.26 1.45 > 80.00 1.15 1.33 > 75.00 1.05 1.20 > 70.00 0.96 1.07 > 65.00 0.86 0.95 > 60.00 0.78 0.83 > 55.00 0.69 0.76 > 50.00 0.61 0.66 > 45.00 0.54 0.58 > 40.00 0.48 0.48 > 35.00 0.42 0.39 > 30.00 0.36 0.32 > 25.00 0.29 0.27 > 20.00 0.24 0.21 > 15.00 0.19 0.17 > 10.00 0.14 0.13 > 5.00 0.09 0.09 > 0.00 0.05 0.05
Message
Re: Densitometry Help
2002-04-23 by flyfishingusa2002