[filmscanners] RE: opinions? Reviews? of Primefilm 1800 ?

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

> Depending on the current levels, so you have the devices original density
> range which, I would suggest is non linear in that for equal variations in
> illuminamnt you will not get a simlar variation in current except probably
> somewhere in the "middle" of the devices sensitivity range.
> At the highlight and shadow light levels the CCD will most likely be non
> linear, rather like film and paper emulsions.

Dickbo,

You can suggest that, but it's not true.  Go take a look at some CCD data
sheet and check the linearity curve.

The Kodak 14400 has a linearity from 0-100% (35 electrons to 230,000) of
+-1%.  It looks nothing like a film curve I have seen.  It's simply a low
slope upward curve starting at 0 (with a little dip), going up to .6% at the
 %50 point and back down to 0 at the %85 point and then going to -1 at the
 %100 point.

> It is considered normal in electrical photo sensitive imaging devices, to
> assume that where random electrical noise equals image electrical
> output you
> will have reached the limits of image shadow response for any
> given imaging
> device.
> At the other highlight end where no further increase in current is
> generated. you have reached the upper limits of highlight reproduction.
> Please note we are talking negatives here baby doll.

That's all well and good, but that is very dependant on ILLUMINATION.

> Bit depth therefore is the same for any particular original
> intensity level
> except that where device response limits are reached at both ends of the
> illumination intensity scale, having say 12 bits or 48 bits per colour
> channel will not enable you to "see" any more visual information because
> there is non to see, at least not once the illuminant has been digitised.

That depends on the design of the scanner.  Again, illumination intensity
AND exposure time play a very important factor in this.

> And that, as they say, is broadly how things work in digital imaging
> scanners.

VERY broadly...and loosely.  There is a lot missing.

Austin

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