Archived posting to the Leica Users Group, 2001/01/09

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Subject: Re: [Leica] 90mm recommendations
From: Johnny Deadman <>
Date: Tue, 09 Jan 2001 10:11:06 -0500

on 9/1/01 7:55 am, Dante A. Stella at wrote:

> As far as I can tell, T400CN has 15 stops of contrast.  I thought that
> translated into more bits (since it's about 1 bit per zone).  At any rate,
> it should be scanned in 16-bit color and then squashed into one color
> channel, but that was not practical, given the color corrections and
> ultimate file size target.  Maybe there is a better way to express this.
> T400 has no shoulder for about 15 stops.

I think you have the wrong end of the stick here, Dante. You can scan
contrasty negs at 8 bits just fine. It's all down to the scanner's Dmax. The
scanner MAPS the neg contrast into 8 or 12 or 14 or 16 bits. The number of
bits doesn't tell you where the scanner gives up on a dense neg... that's
what the Dmax tells you. Otherwise a 16-bit scan from a Dmax 3.0 scanner
would capture a greater dynamic range than an 8-bit scan from a Dmax 3.4
scanner, which is not the case. The extra bits give you finer gradations
between Dmin and Dmax, not a greater Dmax.

The blown highlights on the models nose are either a sign that the density
of the negative is greater than your scanner's Dmax, or that the white point
is clipped (most likely, as most scanner software deliberately does this).

- -- 
Johnny Deadman