[filmscanners] Re: Dynamic range question

["Berry Ives" <yvesberia@earthlink.net>]

Austin, with respect to your last sentence, isn't the point really that the
contrast range of negative film is greater than slide film?  What I mean is
that you can lose either the shadows or the highlights, but slide film
requires more precise exposures and is more limited in the range that it can
handle.  Where I live and shoot, there is great contrast (high elevation
southwest desert), and I think that is one reason for me to shoot negative
film.  I never lose either end that way with the great latitude of negative
color film.  But I'd like to hear what disadvantages there may be to this
approach, if any, in my situation.

Still waiting for the right DSLR for me...

Berry



On 3/25/05 4:45 PM, "Austin Franklin" <austin@darkroom.com> wrote:

> 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
>
>
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