Re: Digicam

[Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>]

In article <3D02C440.ADAE8B1E@bway.net>, SKID Photography
<skid@bway.net> writes
>"Paul D. DeRocco" wrote:
>
>> Even with Kodachrome 25, a tripod, and a fixed focal length lens, I don't
>> believe there's ever 8000dpi worth of actual picture information on a piece
>> of film.
>>
>
>Paul,
>Then you would be wrong.  There is well over 40,000 dpi in a piece of 35 mm
>film.   This has been discussed ad nauseum on several other lists and that has
>been the conclusion, every time.   I don't wish to repeat it here.
>
Harvey,
        whilst there may well be over 40,000dpi of information present
on a frame of high resolution 35mm film, there certainly is not ever
anything close to that in actual image information, which is what Paul
was referring to.

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!
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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