Re: Digicam

[Wire Moore <wirem@xxxxxxxxx>]

on 6/9/02 6:35 PM, Kennedy McEwen at rkm@kennedym.demon.co.uk wrote:

> In article <3D03F50D.74C768AA@bway.net>, SKID Photography
> <skid@bway.net> writes
>> But I think the grain *is* the image, so we agree to disagree.
>> 
> Well, the grain is just the random alignment and clustering of silver
> halide crystals and dye clouds - so presumably you consider them to be
> the image as well.  That's another two or three orders of magnitude on
> image detail.  Then there are the atoms in each crystal - presumably you
> think they are the image as well.
> 
> Somewhere along the line the image information stops and what remains is
> the media detail, not image information.
> 
> Image resolution is NOT limited by grain alone - indeed film resolution
> rarely, if ever, reaches the level of visible grain.  Again, I suggest
> you examine some of the Kodak technical data sheets for their
> professional films, where much of this is explained in some detail and
> where you will find the grain index is not a measure of film resolution.
> If you take the time to run a few comparisons, you will find that grain
> is not even related to resolution, with some fine grain films having
> less resolution than larger grain alternatives.
> 
> So no, we don't agree anything - grain is NOT image and has little
> influence on the limiting resolution of an image on film other than as a
> coarse guide.

Kennedy is on the right track IMO.

This reminds of a certain discussion about 'pixels'; what are they? Do they
have an extent? etc... :)

As is often the case, folks are arguing about a definition of a term, not
about associated principles or practices. In this case, the argument arises
from differing meanings of the word 'image'.

Kennedy considers image to be the information captured from the scene wt
which the camera is pointed, while Harvey considers image to mean the
physical extent of film.

I think most users want systems to capture, transform, and present
information about scenes, not virtualize the physics of a piece of film.

While Harvey cannot be wrong, by definition, I should prefer that Kennedy's
meaning be used in general, and especially by anyone designing scanners
because it leads to a degree of understanding that makes electronic imaging
systems effective. A designer laboring under Harvey's meaning will pursue a
system to recreate the exact structure of the original film, which I believe
to be ineffective by reason that the pursuit is irrelevant to most users.

Wire Moore

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