RE: Digicam

["Paul D. DeRocco" <pderocco@xxxxxxxxxxxxx>]

This is interesting info. Are these rolloffs caused by the random variations
in the grain size? Or is it related to diffusion in the emulsion?

And yes, I did mean to emphasize image detail, as opposed, say, to flawless
reproduction of the shape of each grain.

However, I guess I have to admit that with the finest grain film, a perfect
f2 lens, a high contrast flat subject perfectly focused, and a tripod, it is
possible to get some image detail that will be captured by an 8000dpi
scanner but missed by a 4000dpi one.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

> From: Kennedy McEwen
>
> I suggest you take a look at some Kodak MTF curves for their colour
> films which generally show an MTF down to 10-15% at 120cy/mm maximum,
> falling at an order of magnitude every 10cy/mm or so.
>
> (E100S is at:
> http://www.kodak.com/global/en/professional/support/techPubs/e164/f002_02
> 17ac.gif )
>
> Kodachrome 25 was down to 10% MTF at 100cy/mm, E100S is 10% at only
> 70cy/mm.  A Fuji Provia 100F data sheet specifies the resolution at
> 1000:1 contrast (ie. much more than the typical fine detail in an image)
> of 140l/mm (probably meaning 140cy/mm, though) and only 60l/mm for a
> more typical 6:1 contrast object.
>
> Similarly, even a perfect f/8 lens has an MTF of only 50% at 100cy/mm
> and 10% at 200cy/mm, falling to zero at 250cy/mm (green light).
>
> Even assuming the best development, a high contrast object, the finest
> optical system possible and absolutely no camera motion during the
> exposure, the best we can realistically expect on the film is around
> 150cy/mm for the finest visually detectable detail.  Given the Nyquist
> sampling requirement of two pixels per cycle, this is 300pixels per
> millimeter, or approximately 7500dpi - at which level the detail will be
> no greater than the noise floor on even the best theoretical scanner!
>
> Yes, there may well be detail on film at 40kdpi, but it certainly ISN'T
> image detail!

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