Digital BW, The Print

I can answer some of this. Disclaimer: I'm bad with off-by-one 
errors. 

Each stop is twice as much light as the previous. So we will be 
working with powers of two here. For digital, an N-bit sensor has a 
range of 2^N -1 values. Because it's linear in response (no toe or 
shoulder in the curve, it's just a straight line), zone 0 falls on 
2^0, zone 1 falls on 2^1, etc. So you see where we might get 11 zones 
for a 12-bit sensor such as those found on the 1Ds.

But that linearity bites us because the total number of possible 
tones in between zone 0 and 1 is 2 (2^1-2^0), while the total number 
of possible tones between zone 10 and zone 11 is 1024 (2^11 - 2^10). 
In other words, your shadows have no smooth tonality and the 
highlights get them all. (hence the rule when shooting digital: 
expose such that the histogram is shifted up as far as possible w/o 
clipping objects of interest).

Dmax can be seen as the base-10 logarithm of the total number of 
stops of light. For our 12-bit camera, Dmax=log(2^12 -1)=3.6. 
Scanners pretend to have a Dmax of 4.8 because they have 16-bit 
ADC's. In reality the light source is probably not bright enough to 
properly read that kind of density. Plus, there is inherent noise in 
the ADC's (usu. at least 1 bit).

Some may think otherwise, but I don't think you need to worry about 
your printer's Dmax when shooting. Photoshop can adjust your high-
contrast scan/capture into a lower-contrast printable version. Just 
remember when you shoot digital or scan, that the bottom end of the 
histogram is kind of worthless as far as tonality goes.

-Pieris

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale 
<stevekale@b...> wrote:
> Ok so I must confess that this and the other responses blew 
straight over my
> head, not being a zone guy and not understanding film shoulders and 
toes.
> Can I ask some basic questions so that I can follow the discussion:
> 
> 1)  You speak of 15 stops from colour negative film.  I have heard 
people
> saying that Velvia slide film has just +/- 1 2/3 stops, or 3 1/3 
stops, of
> workable range.  Are these measurements of the same thing?  (What 
is the
> tonal range of Provia?)
> 
> 2) How does one convert stops to density? Loosely.  For example, if 
a
> scanner has a rated dMax of 4.8 how does that relate to the tonal 
range in
> stops of film that it is going to scan?
> 
> 3) Where does the "12 stop linear capability of some censors" come 
from?
> What is the figure for the 1Ds MK II or 1Ds?
> 
> 4) I think I understand the importance of linearity - kind-of-sort-
of - from
> printing.  Is this a similar concept? Ie evenly distributed tonal 
range?
> 
> 5) At the end of the day we are severely constrained by the tonal 
range
> capability of our printing.  Hogarth mentioned 8 stops for silver 
gelatin
> paper.  How do I relate a linearised print of a step wedge on HPR 
with a
> paper white dMin of .04 and a best black dMax of 1.68 to these 
figures?
> (Wouldn't it be nice if they all used the same scale?)
> 
> While the boundaries of the digital print are expanding, I guess we 
still
> need to shoot by compressing the tonal range of the scene with ND 
filters
> (or multiple exposures) so that it can be rendered well in the 
print -
> traditional or inkjet.  I am trying to relate the two (and the 
steps that
> may be in between eg scanning) so that when I get out my spot meter 
I am not
> only thinking in terms of stops but also in terms of my printer's 
tonal
> range.  Sorry if these are basic questions but I think it will help 
a lot of
> people tie all the talk of dMax back to the camera itself.
> 
> 
> Thanks
> 
> Steve
> 
> PS:  this was not meant to be a digital capture vs film capture 
discussion -
> I think the topic relates to both. I do believe there are 
significant
> workflow efficiencies with digital cameras and I am about to make 
the switch
> but relating the tonal range of a scene as measured by a spot meter 
in
> f-stops back to the tonal range of the printer, ink and paper 
combination
> applies to both forms of capture.
> 
> 
> > From: <claudej1@a...>
> > 
> > 
> > 
> > Boy, you have opened a big can of worms here. Most of the color 
negative
> > film (normal C-41 development) has a Contrast Index of 0.44-0.52, 
which means
> > a  
> > 1 stop luminance change in the scene records a 0.14 change in 
density in the
> > film. Assuming no major color crossovers, from a pure 
monochomatic conversion
> > of  the resultant lumped densities, you can get out to about 15 
stops of
> > luminance  before a shoulder apperars from the straight line and 
short toe of
> > color 
> > neg.  films. This from a Dmin in the shadows of about .25 to a 
Dmax of r 2.38
> > in the  highlights.
> >  
> > B&W films, especially Tmax (per my curve tests circa 1990) can 
vary  from
> > 3-11 stops with D-76 straight (I wild combinaton to tame I might 
add) and a
> > 5-11 
> > minute development time. So with B&W, the Contrast Index (CI) 
varies  with
> > development, as does the effective shadow thresholld speed, 
although not as
> > much as you might think.
> >  
> > ISO states that you need a CI of 0.65 to get the box speed 
rating. Most
> > Zoners develop their filme to a CI of 0.55 to match to the CI of 
#2 paper,
> > which  
> > is a CI of 1.8 in an ideal world. So ISO essentially "pushes" the 
film a
> > little  to get their rating, but real users have always derated 
their film at
> > least 
> > 2/3  stop with their "normal development."  So, with severe speed 
derating
> > and  an extreme development "pull" you can get a lower CI than 
color neg.
> > film, 
> > which  is fixed. This could also inhibit the Dmax of the film 
depending on the
> >  developer and how it is agitated.
> >  
> > I have achieved densities in excess of 4.0 with Tmax developed in 
Dektol
> > (not a misprint), but I never tested for linearity.
> >  
> > So, the recordable density range for B&W film varies all over the 
map  and is
> > not necessarily superior to the 12 stop linear capability of 
some  sensors.
> > Besides, with digital capture, you can easily increase the 
dynamic  range with
> > a separate highlight and shadow range exposure to be blended 
later in  any
> > ratio you wish.
> >  
> > This makes blanket statements, in either case, untrue without 
specific
> > details of each method.
> >  
> > I prefer the speed and efficiency of digital capture with the
> > creative/corrective post processes afforded by Photoshop, but 
that's just me.
> > I'm too 
> > impatient to go back to the darkroom for any reason. I earn my 
living  with
> > "click 
> > to print" workflows of less than 1 minute for a 4x6 color print 
from  high
> > speed dye subs, and I'm starting to do the same with Epsons, so 
maybe I've
> > been 
> > pulled too far the other way by digital technology.
> >  
> > I simply love color pigments AND BO/Quad/Hex/Sept/Oct monochrome 
inkjet
> > output on various papers. What a great time to be in 
the "lightroom" with so
> > many 
> > great choices.
> >  
> > My handcuffs are long gone along with my toxic chemical 
dependency.
> >  
> > Claude
> > 
> > 
> > [Non-text portions of this message have been removed]
> > 
> > 
> > 
> > 
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