RE: [Leica] Print film scanning D-Max?

["Austin Franklin" <darkroom@ix.netcom.com>]

Hi Tim,

Sure, I'd be happy to 'splain it.

First dRange...  The "d" means density (and has nothing to do with dynamic
range), and when measuring density that film records (as in contains valid
image data), there is a minimum value (dMin), and a maximum value (dMax).
The range between these two density points it the density "range", or
dRange.

Positive film has a clear base...so the dMin for it is going to be quite
low...as compared to negative film, which has a cloudy base...so the dMin
for negative film will be quite a bit higher than positive film.  Both films
will pretty much have the same max density, black is still black, whether
it's positive or negative film.

Well, let's say the dMax (blackest part) of both films can be measured at
3.6...and the positive films dMin is .2, and the negative films dMin is
.8...  That gives a dRange for the positive film of 3.6 - .2 or 3.4, and for
the positive film 3.6 - .8 or 2.8.

It's purely the film base "offset" that creates the difference in density
range.

For another discussion (after this one if you like ;-)...let's say that the
same range of image tonality could be recorded on either film...just that
negative film would have the range compressed, film density wise that is,
compared to positive film.  Also, the "dynamic range" of the film is not the
same as the density range...and the term dynamic range is often misused when
talking about density range.

Regards,

Austin


> Thanks Austin,
>
> I meant more along the terms of how did you explain it rather than justify
> it...!
>
> Could you explain what you mean by dRange and what this means for
> scanning.
>
> thanks
>
> tim
>
>
> > > Was it on the LUG that someone posted that negative films only need a
> > > scanner d-max of 2.8 or some such?
> >
> > Hi Tim,
> >
> > Yes, it twas I who posted that some such ;-)
> >
> > > Also, if so, what was the rationale?
> >
> > Do you mean what do I base my claim on?  20+ years of measuring
> > film with a
> > densitometer...as well as over 10 years of scanning film...
> >
> > Technically, it's not dMax that matters, but dRange...and often
> people say
> > dMax when they really mean dRange...or they simply reference dMax
> > to a dMin
> > of 0, and therefore dMax and dRange are the same.
> >
> > Austin

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