[filmscanners] RE: Dynamic range question

["Austin Franklin" <austin@darkroom.com>]

Hi Bill,

> It's been several years, but I seem to remember that when I got my
> Nikon 4000ED filmscanner they were claiming a Dmax of somewhere
> around 3.5 to 4.0, but I measured it (by scanning a Kodachrome IT8
> target slide and examining the greyscale separation)  at around 2.1
> to 2.9 (don't remember the exact number).  This kind of disparity
> between manufacturer's claims and real-life performance is the rule,
> not the exception.

>From what I can tell from your post, what you did was measure the density
range of the IT8 slide, correct?  If so, then that is what you measured, the
density range of your IT8 slide...that may or may not equal (or closely
equal) the dynamic range of the scanner, they are two different things, and
are not necessarily a 1:1 correspondence.  That is a whole can of worms unto
it self.

It is true, that typically manufacturers who make claims of 4.8 are simply
stating the bit depth of their A/D converter, and their A/D converter is 16
bits (log 2**16 is 4.8).  As has been said, the dynamic range (and density
range) of the scanner is typically limited by the CCD, and not the
electronics.  Manufacturers of CCDs do publish the noise numbers of their
sensors, and if you could find out what sensor they are using, you could
find out from the sensor's specs what the manufacturer claims the range is.

Also, unless you are scanning slide, the dynamic range/density range of the
scanner will not be prohibitive for most any modern scanner.  And, for
negative film, it has nothing to do with being able to "pull out the
shadows", as the shadows on negative film are the light areas, not the dark
areas.

Regards,

Austin


----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body