Digital BW, The Print

Austin,

Merriam-Webster's Collegiate Dictionary:
"Main Entry: dynamic range
Function: noun
Date: 1949
: the ratio of the strongest to the weakest sound intensity that can be
transmitted or reproduced by an audio or broadcasting system"

In visual terms the ratio of black to white which we think of in terms of
Density (Dmax and Dmin), which is a base 10 logarithmic expression of the
inverse of the amount of light reflected from the surface of the print.
(While this was once convent for mathematical calculation it is not
intuitive way to look at the data.)

Density = log(1/reflectance) Reflectance being the amount of light reflected
by the ink and/or paper

Typical inkjet print has Dmax of 1.4 to 1.7 (4.0 to 2.0% reflectance)

Typical silver print has Dmax of 2.2 to 2.6 (0.6 to 0.3% reflectance)

Similar Dmin values in the 0.02 to 0.06 range. (95.5 to 87.1% reflectance)

Calculated using Dmax and Dmin:
Inkjet dynamic range:  23 to 85
Silver dynamic range: 36 to 130

Calculated using Reflectance %:
Inkjet dynamic range: 22 to 48
Silver dynamic range: 145 to 318

Of greater interest:

Calculated using the difference in Dmax and Dmin:
Inkjet range:  1.34 to 1.68
Silver range: 2.14 to 2.54

Calculated using the difference in Reflectance %:
Inkjet range: 83.1 to 93.5
Silver range: 86.5 to 95.2

One of the things we often neglect is the importance of Dmin. Most of the
inkjet papers have a better (lower) Dmin than silver papers and this has a
strong impact on the dynamic range and range. I think that the range of the
reflectance is most informative and indicates that the difference between
silver and inkjet is not as great as log values suggest.

For instance here are some comparisons of Density values to Reflectance
values:

      Density Reflectance
      0.01 97.7%
      0.02 95.5%
      0.06 87.1%
      1.4 4.0%
      1.7 2.0%
      2.2 0.6%
      2.3 0.5%
      2.4 0.4%
      2.6 0.3%


Small changes in the Dmin make very large changes in the maximum reflectance
of the paper while big changes in the Dmax have little impact on the
reflectance of the blacks. The difference between a density of 0.02 and 0.03
are easily seen by the human eye but we have a difficult time distinguishing
between densities of 2.4 and 2.6. The reflectance values show why this is
the case.

The big step we see in comparing ink and silver is that 1.7 to 2.2 step, a
change of only 1.4% in reflectance but quite noticeable. I believe this is
largely due to the matte vs. smooth surfaces. The difference between inkjet
and silver matte paper at this point is probably very small.

Several people have pointed out the differences between inkjet and silver
Dmax are largely lost when the images are framed and placed under glass or
plastic. I have also found this to be true.

I don't think you can prove an inkjet print has more tones than a silver
print because it doesn't. Since a silver print and an inkjet print are both
analog, there is an infinite number of tones between the minimum and
maximum. This is true independent of our ability to measure or visually
resolve adjacent tones past a certain degree of similarity. It is based upon
the fact that any line segment regardless of its length has an infinite
number of points. This means that both are infinitely capable of expressing
whatever we want within the outer limits of the range.

You suggest that inkjet offers a larger palette of tones and there is no
empirical evidence to support that.

But this is where I came in a year ago and you and I beat it to death then
without agreeing so I vote to agree to continue to disagree.

Martin




----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Sunday, March 24, 2002 9:29 AM
Subject: RE: [Digital BW] Dynamic Range


> > Austin
> >
> > My old fibre based prints are very similar in density ratio to
> > inkjet on cotten. They were never as "snappy". Do you think the
> > dynamic range of inkjet would be akin to fibre based?
> >
> > Garry Sarre
>
> Hi Garry,
>
> I believe, though I have not proven it with any tests of my own, merely
> personal observations of images printed using both, that inkjet prints can
> produce more tonal variations than wet darkroom, and therefore have a
higher
> dynamic range.  It's probably an easy thing to "prove" using a step wedge.
>
> Regards,
>
> Austin
>
>
>
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