Digital BW, The Print

You might want to take a look at the document, RGB Scanning Guide, by Don Hutcheson 
(available on his website http://www.hutchcolor.com or in the files section of Yahoo 
ScanHi-End).  On page 5 there's a table that shows typical values for RGB, Luminence and 
Density. The information is for transmissive readings but it illustrates the non-linear nature of the 
luminence/density relationship.  With overall density ranging from 0 to 4.0, medium gray 
translates into a density of about 0.7.

- Tom Dunn

--- In DigitalBlackandWhiteThePrint@y..., "chervinsky02144" <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