Re: filmscanners: film vs. digital cameras - wedding/commercial photography

["Karl Schulmeisters" <karlsch@earthlink.net>]

----- Original Message -----
From: "Austin Franklin" <darkroom@ix.netcom.com>
To: <filmscanners@halftone.co.uk>
Sent: Thursday, August 16, 2001 8:21 PM
Subject: RE: filmscanners: film vs. digital cameras - wedding/commercial
photography
> It would appear you agreeing with me by saying that "creating additional
> data points is the result of an interpolation".  You obviously understand
> the point.  As I said, the digital cameras (aside from the Fuji) do not
> create additional data points, they only changing the values of these data
> points.  I believe we disagree on whether this is really interpolation or
> not.


I do believe this is the disagreement.  if a Red-Green diagonal crosses this
"GRGB Quadrulplet" - and the software tries to figure out what the Red and
Green values should be for the two sub-pixels outside of the actual
diagonal, there are significant pathological cases where it will get it
wrong.

So from a photographic perspective, a Pixel, is the whole Quad - which is
why the Fuji isn't really a 6Mpixel camera (even though it reads 6 Million
dots).

Also earlier you said

>Karl, I'm not buying the above resolution/zone claim.  Of course MF film is
>larger than 35mm film, that's why it's MF, but I do not believe that the
>lp/mm changes between zone III and zone VI.

I refer you to the latest issue of PhotoTechnique and its article on Gigabit
film.  If you think about the physics of how film works, a drop in LPMM
resolution as inbound light intensity drops, makes a great deal of sense.
FGZMPLE lets assume it takes 10 photons to "flip" a silver-nitrate (or
whatever silver compound is in use) crystal (yeah I'm simplifying a bit
here).

So the LPMM resolution in Zone VI is controlled by the density, size and
diffusion of the silver crystals since there is ample light to flip the
photons in the 'white line' and just below the threshold to flip the black
lines.

Going down to Zone III exposure the crystal parameters are the same, but the
number of inbound photons is significantly reduced.  Given random photonic
distribution, the likelihood that enough adjacent crystals in the 'white
line' will flip to be measurably more opaque than film fog, goes down.
Since the probablity goes down, the actual number of times it happens in the
aggregate goes down.  What that in effect means is that the 'white/gray'
line, becomes a series of dots, not a well defined line that 'counts' in
LPMM.

Now if you widen the line, the likelihood that enough crystals in the region
of the line, sufficient to actually create a 'contiguous' line will flip,
goes up.  Why?  Because the probability of a single crystal flipping stays
the same, but the number of crystals involved goes up, and hence the
aggregate probability of actually recording the line, goes up.  But a 'widen
the line', in essence you are decreasing LPMM.  So in Zone III, the LPMM
will be lower - and from what I have read and seen, empirical data bears
this out.  Heck my personal experience with changes in my eyesight as I age,
bears this out.

Stuff I could read as a kid in shade light, I now need to shine a flashlight
on to read.