Digital BW, The Print

On 3/29/02 10:39 AM, "Austin Franklin" <darkroom@...> wrote:

>> 1.  I now think you do need both density range and dynamic range to
>> characterise the tones in a print.  Clearly the blackest black is
>> important
>> and the whitest white is important -- these are measured by their density
>> and the difference would be density range. Also the ability to
>> render smooth
>> transitions from one tone to another across the density range is important
>> and this would be measured by Dynamic Range.
> 
> Bingo!  And very eloquently worded.  I hope it didn't take too many licks to
> get there ;-)
> 
>> 4. The dynamic range of my prints (using the piezo driver v5, and epson
>> 1200, and MIS FS inks) has a maximum of:
>> 
>> -10log10((measured paper black density)-(measured paper white
>> density)/256))
>> 
>> Since the originating image only contains 256 shades of grey this caps the
>> upper limit (ie smallest value of) on the minimum perceptible
>> change.
> 
> You are correct, assuming your print HAS 256 tones though.  They dynamic
> range of the printing system would always be 256 tones, but the print does
> not have to contain 256 tonal steps, or 1/256th step per tonal variation.
> Printing litho film comes to mind.
> 
>> If my
>> eyes can only perceive 100 shades of grey then the dynamic range is lower.
> 
> I don't believe that lowers the dynamic range of the print...it is what it
> is.  The dynamic range YOU can perceive is lower, no doubt.
> 
When you say "it is what it is" do you mean that given a set of increasingly
accurate measuring devices there will be a point where the next most
accurate device will not yield a result different from its predecessor?

Also, how do you deal with the increasingly precise measurement when the
precision of the measurements starts to exceeds 2x (or is it 1/2) the
physical characteristics of that which you are measuring (ink droplets,
silver grains etc.

>> If my eyes can see 1000 shades of grey the dynamic range is still
>> capped by
>> the 256 shades that the print originated in.
> 
> Very true.
> 
>> To assess whether a silver print has more or less dynamic range you would
>> have to use a "system" that can accurately discriminate as many distinct
>> tones as our eyes and see if either print reaches its discrimination limit
>> before the limit of our eyes is reached.
> 
> Some prints are blatantly obvious though.  I don't know that you need to
> factor our eyes into this, as you really need to use a measurement technique
> that is more accurate than what it is you are trying to measure.  As you
> have said, our eyes can only distinguish 100 levels of gray (in any one
> lighting condition that is).
> 
> Regards,
> 
> Austin
> 
> 
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