Digital BW, The Print

> 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.

> 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