Digital BW, The Print

----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Sunday, March 24, 2002 11:28 AM
Subject: RE: [Digital BW] Dynamic Range


>
> > 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"
>
> Hi Martin,
>
> Yes, that's pretty much correct.  It is the largest measurable signal over
> the noise, which is the minimum measurable signal.  This is so, basically,
> as you can not measure smaller than the noise in the system, so the noise
> becomes the "step" within that system.

Austin,

The Merriam definition takes this into account as the "weakest sound
intensity" would be the sound just greater than the noise floor.
>
> > 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.)
>
> Correct.
>
> > 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
>
> No...that's the point.  Density ratio values are NOT the same as dynamic
> range.

That's not what the definition says.

 The value of 1 is the step size of density ration values, but NOT of
> dynamic range.

Density variation is step-less in an analog system. A silver print is a
continuous tone image.

 "1" is nothing but a ratio value, as in, 2:1 is twice as
> dark...  Technically, something can be 1.223456:1 times as dark, but the
> density ratio value system is based on :1, and does not accommodate
this...
>
> Dynamic range requires you know the noise in the system,

This is true in audio and electronics but seems to have little to do with a
step wedge of tones on a piece of paper.

>  density ratio
> values do not, they are only relative to themselves in intensity, where
> dynamic range is not.  As the example I gave in my other post, you can
have
> a really high density value of, say 4, but no tones in between...and that
> has poor dynamic range, but you can have a dMax of 1.8 and a dMin if .1,
but
> have a whole lot of tones in between...that has a high dynamic range.

Dynamic range does not tell you anything about what is in between the end of
the scale it simply defines its scope. If it is analog you can stop anywhere
within the range an find a point and those are infinite in number. Silver
printing is stepless.
>
> > One of the things we often neglect is the importance of Dmin.
>
> I don't ;-)  Most people assume when a dMax value is stated, dMin is 0.
> That isn't always true, obviously.
>
> > 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'll go back to my original statement.  Density ratio values have nothing
to
> do with dynamic range.  They are entirely different.  Therefore, because
> silver has a higher dMax (which I do not dispute), does not mean it has a
> larger dynamic range.

No max:min density ratios are dynamic range. I will stick to the dictionary
definition. You are arguing less is more.
>
> > I don't think you can prove an inkjet print has more tones than a silver
> > print because it doesn't.
>
> Absolutely can.  Technically, inkjet can reproduce an infinite number of
> tones, since it is using a dither pattern, and all you have to do is make
> the image large enough (or dots small enough), and the dither pattern
> accordingly, and you can make infinite tones.  We are specifically talking
> about printing now, not the film or scanner etc.

Yep infinite tones.

>
> > Since a silver print and an inkjet
> > print are both
> > analog, there is an infinite number of tones between the minimum and
> > maximum.
>
> Well, no.  The silver print is finite, since noise will overcome your
> ability to discern tones.  That's what limits silver prints dynamic range.
> The number of steps that can be discerned (in a range) is dynamic range.

Okay, if it is finite how many tones can be produced in a silver gelatin
print?

Silver is not finite. Silver emulsion exposure and development produce
reactions that can proceed to any point and provide an infinite number of
tones.

Since you are looking a print, either inkjet or silver, the "noise" if any
will be the same. The ability to discern steps is a limit of your measuring
methods or your eye not of the system, and the same situation exists for
both.
>
> > 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.
>
> Don't give up on me, I know my "position" can be understood if I explain
it
> well enough.  I believe this IS a very very important point for
discussion,
> and I am very happy to continue it.  It is probably the most
> misunderstood/discussed issue, and the terms Dynamic Range and Density
Range
> are used interchangeably, and they are not interchangeable, as I believe I
> have shown...or at least attempted to show.

I understand, I just don't agree. I think that you are redefining dynamic
range in light of your electronics and digital background that are not
completely applicable to a paper print.

I agree that Density Range and Density Dynamic Range are not
interchangeable. Range is the max minus min difference and Dynamic Range is
the max:min ratio.

In any case, neither value places a limit on the ability to make a fine
print with the materials chosen, either ink or silver.

Best
Martin