Digital BW, The Print

Barry,

If dmax is 1.8 and dmin is 0.05 then the Density Range is 1.75.
To find what percentage of the Density Range .6 is divide .6/1.75=0.34 
or 34%

Mike

On Tuesday, April 23, 2002, at 08:31 PM, flyfishingusa2002 wrote:

> 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
>
>
>
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