On 9/5/12 8:54, John Francis wrote:
On Tue, Sep 04, 2012 at 10:26:07PM -0400, John Sessoms wrote:
I really like the concept behind the Foveon sensor - every
photo-site captures all 3 colors like film did& no need for the
anti-aliasing, but what's the deal with the poor image quality above
ISO 400?
Physics. If you don't have separate sensor sites for the three colo(u)rs,
then the photons for two of the colours have to pass through at least one
of the layers that contain the sensors for the other colours.
To oversimplify the situation, you can't create a sensor that captures all
the blue photons, and yet lets 100% of the red or green photons pass through.
As a result, the second and third layers don't receive 100% of the photons
that they would respond to if they were the frontmost layer. This leads to
a degradation in sensitivity and in the signal-to-noise ratio.
Quite. Like I sort of said elsewhere, though, it seems to me that you
could pass through a lot less than 100% and still be better off than you
are when filtering at every site.
Also, maybe there is actually more noise, too, and not just less signal
- as a result of more complex read-out circuitry or whatever...
- Toralf
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