John A. wrote:
On Mon, 09 Feb 2009 17:09:50 -0500, ASAAR wrote:

On Mon, 09 Feb 2009 21:34:29 GMT, John A. wrote:

And a pixel IS made of 2x2 photosensors on a Bayer-filtered sensor
array. The sensors are arranged something like this:

G R
B G

Together, those four photosensors make up one pixel.

Ahhh... But I think I see what you're talking about. That's in a
single-exposure Bayer system. In the theoretical four-exposure system
we are discussing we would get four three-color synthesized pixels
from each 2x2 Bayer array. (Minus a row and a column for the image, I
believe, assuming we'd only keep the overlapping portions of the four
exposures.) That was what you meant, right?

So maybe we both get it, and don't get it. =D
Gotcha! But no, the
G R
B G
photo sensors don't make up one pixel. If they did, then a 12mp
sensor would have 48 million little silicon RGBG thingies. Some
advanced amateurs have been known to physically remove the bayer
filter, using powerful solvents to dissolve it. A de-Bayered 12mp
sensor then becomes a monochrome 12mp sensor, not a 48mp sensor.

In a way, the Bayer filter cheats a bit. The intensity of each
colored pixel is calculated by interpolating (demosaicing) the value
of the light that it registers as well as that of the differently
colored pixels that surround it. The result isn't 100% accurate,
but it's more than good enough. Seeing is believing!

Dissolving the filter doesn't change the circuitry and firmware. The
camera still interprets the 2x2 sensor array as one pixel.

The raw file has the separate bayer parts unmerged.

I'm not sure how a half pixel shift would work for increasing
resolution... perhaps you'd need to go 1-1/2 or 2-1/2 pixels.

--
Paul Furman
www.edgehill.net
www.baynatives.com

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