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RE: filmscanners: Magnification of light



Austin wrote:

>Think of it like your hearing...now that you're older, you can't hear high
>frequencies, but when you were younger you could...yet the amplitude of the
>high frequencies hasn't changed...  That is because as you get older, the
>dynamic range of your ears decreases.

Oooh, you really know how to hurt a guy, don't you? ;-)

>Do you know what DMax means, mathematically that is?

I had to work *very hard* to keep from flunking math, but managed A's. Not 
like I understood it or anything. ;-)

But yes, as I understand it (scanner-wise), DMax is the maximum amount of 
density a CCD will recognize and record from a piece of film as "Black." 
DMin is the maximum amount of light (non-density) a CCD will recognize as 
"White."  The Density Range is what lies between. A bit of dust on a neg 
will block and transmit little if any light to the receptors, and be white 
when the scanner interprets it as a negative light generation and reverses 
it's light transmisibility. A similar mote of dust will translate as "Black" 
on a slide. Neither of these will be either "Black" nor "White," but will be 
*percieved as being. An example once given was a black cat against the sun 
as a background--what scanner could get that? Or what film, for that matter, 
and preserve that precious little "locket" that all black cats (felis 
domestica, at any rate) have?

I might well have answered the wrong post, but I thought we were discussing 
the "flare" evidenced in dark-light scanned photos, the most extreme of 
which are Harry's astronomy pics and his inspired "pin-prick" experiments, 
which I've done myself with a diferent scanner and diferent results. If I've 
unfortunately blundered into the wrong discussion, then I'll see if I can't 
just segue off-stage-left without falling on my face. ;-)

Best regards--LRA



>From: "Austin Franklin" <darkroom@ix.netcom.com>
>Reply-To: filmscanners@halftone.co.uk
>To: <filmscanners@halftone.co.uk>
>Subject: RE: filmscanners: Magnification of light
>Date: Fri, 15 Jun 2001 16:37:45 -0400
>
>
> > Seems to me that there are *two* factors at work here, not mutually
> > exclusive. The Dmax wouldn't explain why dust effects are amplified--and
> > they seem to be, by empirical observation of several members.
>
>I have no idea about this, but it was not part of what I was talking about.
>
> > Nor
> > would the
> > dynamic range explain why light appears to be magnified in
> > contrast to dark
> > areas (although that's also a function of the human eye, and not easily
> > quantifiable).
>
>Dynamic range does explain that.  In fact, that is what dynamic range is.
>Think of it like your hearing...now that you're older, you can't hear high
>frequencies, but when you were younger you could...yet the amplitude of the
>high frequencies hasn't changed...  That is because as you get older, the
>dynamic range of your ears decreases.
>
>Dynamic range is the breadth of which you can sense.  A wider dynamic range
>of a sensor means it extends its limits either up or down (or both) the
>spectrum.  Since film only has a dynamic range of high 2's to low 3's for
>color print film, and the CCD in the camera has a dynamic range of mid 3's,
>it will be able to discern dark detail better than negative film.  It's
>simple math.  Do you know what DMax means, mathematically that is?
>
> > I might very well be missing something, here,
>
>It could be you may be don't understand what dynamic range and/or density
>ratio values are?  If not, I can explain it...
>

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