Digital BW, The Print

Hi Truman,

> The others also have 1/3 of the
> resolution that they claim.

That's not true.  They have the FULL spatial resolution they claim, it's the
color fidelity that is decreased.  It's a matter of number of photosites,
not pixels or M bytes.

> You cannot invent additional sensors than are not there.

Well, actually you can.  That's what interpolation is...but it wouldn't work
with the Foveon in the same way as it does with the Bayer pattern imaging
sensors, simply because the Bayer pattern imaging sensors have every output
pixel based on some actual data from that photosite.  Interpolating a Foveon
would be the same as doing it in PhotoShop...but the Bayer pattern
interpolation for color information is entirely different.

> Of course if you step a red then blue then green laser across a
> conventional sensor you will get 1/3 the number of sensors advertised.

Actually, 1/2 for green.  The Bayer pattern imaging sensors have %25 red,
%25 blue and %50 green.

But, the fact is, not much exists in real life that is %100 red, %100 blue
or %100 green, and this is why the Bayer pattern imaging sensors give really
good images, and why a Foveon, even of the exact same spatial resolution
size, doesn't give much of an increase in color fidelity over a Bayer
pattern imaging sensor of the same spatial resolution.

People are confusing two resolutions.  One is spatial, the other is color
(tonality).  Spatial is purely based on the number of photosites.  Color is
based on the depth of information received at any one photosite.  For the
Foveon, it gets full RGB at each photosite, and for the Bayer, it gets
either R, G or B at each photosite.

To relate this to your computer monitor.  You can have a 1200 x 1600 monitor
with 8 bits/pixel (256 colors), and the same monitor can be 1200 x 1600 with
24 bits/pixel...yet they are the exact same spatial resolution.  A 768 x
1024 monitor with 24 bits/pixel does not have the same spatial resolution as
a 1200 x 1600 monitor with 8 bits/pixel, though it has higher pixel
depth...but pixel depth is irrelevant as far as spatial resolution goes.

In fact, TV works a similar way to the Bayer sensor concept, where the color
information (Chrominance) is only 1/4th as much "data" as the luminance
information.  This works because of how our (human) visual
acquisition/processing system works.  We are more acute to edge/luminance
difference than to color differences.  This is why there is such a marginal
(if any) true visual benefit to having full color information, like the
Foveon gives.

Austin