On Wed, 19 Dec 2001 00:23:39 -0600 (CST) patton paul
(ppatton@ux1.cso.uiuc.edu) wrote:
> I've also been looking at the
> specs for the Nikon Coolscan IV and Minolta Dimage Scan Elite II. For
> both these scanners, the dynamic range is calculated based on the A/D
> conversion, which is 12 bits for the Nikon and 16 bits for the Minolta.
> log10(2^12)=3.6, which is the stated dynamic range for the Nikon, and
> log10(2^16)=4.8, which is the stated dynamic range for the Minolta.
> Unfortunately, the A/D conversion value isn't given for the Canon
> scanner.
> If the 14 bit value is the actual output then the dynamic range would be
> log10(2^14)=4.2, which is better than the Nikon. On the other hand if
> the
> "8 bit output" is actually the A/D conversion value, then the scanner's
> dynamic range would only be log10(2^8)=2.4, which would explain why they
> didn't list it with the specs. Does anybody know which is the right
> value?
These theoretical values are misleading, since they take no account of CCD
noise, any other non-linearities, optical flare and so on. There's not
much point in choosing a scanner with some exotic quoted OD range if
the last 0.9 is buried in blue snow, or you have to do 16x multiscanning
taking 45mins per image to get rid of it.
Real-world use is the only reliable point of comparison, since there
aren't any agreed standards for measurement.
All these scanners are capable of 16bit/channel file output, or 8 bit if
you tell the software that is what you want. Generally anyone who is picky
enough to want massive ODR will want to work with 16bit files in PS and
reduce the bit depth as late as possible in the processing.
I can't comment on relative quality of these scanners or effectiveness of
the IR dust removal algorithms without having used them.
You missed the Polaroid/Microtek 4000 models off the list - the Polaroid
SS4000 is available at silly prices now, pending replacement by the
SS4000Plus, if you can find anywhere which has stock. No ICE, and 'only'
12 bits, but very little CCD noise.
Regards
Tony Sleep
- Online portfolio & exhibit; + film scanner
info & comparisons
