RE: RE: filmscanners: RE: filmscanners: Pixels per inch vs DPI

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

> Austin wrote..
> >..I DID stick to the
> > ball...please point it out...I am interested.
>
> I'm away from my normal PC right now, so I can't quote the lines
> that I felt were getting personal (a convenient cop-out, I
> know!), but comments like this:
>
> '..but I really don't know what more I can explain...and I don't
> know how much more basic I can get...  Sigh.'
>
> ..are a bit of a put-down in my book.  Perhaps I am just the
> overly sensitive type, but I would be a bit offended if they were
> comments directed towards me.

Those, at least for me, were statements of fact, not in any way meant to be
put downs.  There was nothing personal at all (except a mild expression of
my frustration) meant by those statements.

> Anyway, back to the debate, which
> I hope isn't getting too off-topic..
>
> > But why IS 9 larger than 4?  You didn't explain
> > why.
>
> We have to some basic 'given's', otherwise nothing can be
> discussed... :-)

Absolutely!  That was my point...some things just are because they are.

> > Saying a dye cloud has more information content
> > than A pixel is NOT ambiguous at all, it's just
> > a fact..
>
> Yes, agreed.

And ya should have stopped there ;-)

> But my (and I think Rob's) point is that fact is
> not of much importance unless you are heading for a useful
> conclusion,

Useful or not, it was what I was pointing out...

> There are many factors involved in
> that question, eg over what size area?

Why do you believe that matters?  A dye cloud is the same size, no matter
what format the film is.

> (Why do we use 6x7 instead
> of 35mm? - Because of those darned too-big dye clouds, that's
> why!)  And I'm concerned about recording the image, not dye
> clouds.  In the same way that we use larger format films, and
> smaller dye-clouds as methods to get better images, we can keep
> reducing the size of the 'pixels', and if we meet a physics limit
> (or more often an expense limit), then we can increase the area
> over which that image is recorded.  And that *doesn't*
> necessarily mean huge cameras/lenses, if you think laterally..

Well, actually, it does...to meet the same quality that is.  As I also said,
there can also be a point where one is satisfied that the image meets the
requirements...but that wasn't what was being discussed.  The discussion was
about equivalence, and my point was they aren't equivalent.

If you take my numbers on what you would need for a "rough" equivalence to
film, say 15,240 x 10,160 actual pixels worth of sensors...given that for a
quality sensor, you would need to use CMOS.  The Canon D30 uses a sensor
that is 2226 x 1460 with a physical size of 22.7mm x 15.1mm.  That makes the
sensor elements 22.7mm / 2260 or about 10 microns square, or about 20
microns x 20 microns (for four sensors)...

So, you would need a sensor that is 15,240 x 20 microns in one dimension,
and that is .3 meters, or 13" x 10,160 x 20 microns in the other
dimension...or 8.74"...that's a pretty big sensor.  Even with advances in
technology, that say, pack 4x (four times) the density...you'd still get a
sensor that is 6.5" x 4.4"...still very big.

Also remember, as sensor size goes up, so does the requirement of the size
(diameter) of the lense...

> > I said that physical limitations prohibit
> > sensors from being as small as dye
> > clouds.
>
> As above, this is only an issue if you are trying to match up
> your sensor with some pre-determined film size.

Disagreed.  It's not the film size you would want to match up, but the
quality of the image.  It just gets worse (for digital) as the film gets
larger.

> > AS I said, these sensors have to get
> > light to them
>
> Which can be bent, magnified, reflected, spread...

Area is area...and you need just so much area...bending, reflecting etc.
won't really help.

> > and they have to have wires in and out of them
>
> hmm.  Maybe using current technology they do..
> :-)

And well after your and my death they will too...

> Anyway, as soon as a decent *affordable* 8Mp or better digicam
> arrives, preferably with interchangable lenses and decent battery
> life, I'll be jumping ship and only dragging out the film scanner
> for the 'archives'..  I won't be pining for the days of dye-clouds..

An 8M pixel sensor is really only a 2M pixel sensor, since these sensors use
Bayer pattern sensor arrays (four color channels to make up one pixel, RGBG,
extra G for contrast).  They interpolate the data to arrive at the rest of
the 8M...  Personally, I believe it is entirely fraudulent for the
manufacturers to make the claim they do...since a pixel, by definition, must
contain all three colors, and there aren't 8M sensors for each color...but
2M for each color.

Look, I understand "wild eyed" thinking, speculating and dreaming...and
people thought we'd be on Mars by now, and headed for Pluto...but it ain't
so.  There is a little matter of reality.  I spend my life coming up with
new things and new ways to do things, and I completely understand advances
in technology...but there is also a tempering of expectations that requires
knowledge beyond just the concepts, to really understand what can and can't
be done.

Just to give you an example, the design of my scanner is 12 years old.  None
of the currently available CCD scanners, except the Imacon, can scan 35mm at
the resolution my scanner can scan at.  None.  Not even the new Nikon or
Polaroid.  Why is that?  Because not much has really advanced in 12
years...yes, there have been advances, small and incremental.  Mostly in
processors and memories...but not near as big in scanner technology.  You
would think, by your digital camera thinking, that in 12 years, we went from
a 16MHz 286 to a 2GHz CPU, we should have FAR better film scanners...but we
don't.  They are better, to some degree, but not to the same degree as CPUs
and memories have advanced.  As I said, it's a different ball game with
analog sensors...