Digital BW, The Print

Jeff, 
Thanks for the math! Now here's the question, If Dmax = 1.8 and Dmin 
= 0.05 What percentage of the dynamic range is, say, .6? Can you 
show us how to do it?

Barry

--- In DigitalBlackandWhiteThePrint@y..., "iwasnvrhere" 
<iwasnvrhere@y...> wrote:
>     This might help. 
>  optical density (OD): For a given wavelength, an expression of 
the 
> transmittance of an optical element. Note 1: Optical density is 
> expressed by log10(1/T ) where T is transmittance. (188) Note 2: 
The 
> higher the optical density, the lower the transmittance. Note 3: 
> Optical density times 10 is equal to transmission loss expressed 
in 
> decibels, e.g. , an optical density of 0.3 corresponds to a 
> transmission loss of 3 dB. Def of optical density.
> 
> Jeff
> 
> 
> 
> 
> > 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