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"

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.

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

> 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.

> 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.

> 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.

> 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.

Regards,

Austin