Winsor wrote:
>>
One does wonder that if regular CCDs and CMOS chips do not function
well with wide angle lenses, then the problem may be even worse with
the Foveon X3 when the pixels are stacked even deeper.
<<
Winsor,
It should be very approximately 3 time better for Foveon, because
the normal Beyer pattern reduces the area per colored pixel by approximately
3, while the Foveon chip does not. (stacked vertically rather than
horitontally) This means if the depth of the pixel diffusion layers in the
case of Foveon, are the same as the filter layer of a conventional chip the
shading effect is greatly reduced. The lateral angle of acceptance would be
much greater allowing wider angle lenses. It could be even better than this,
since the sensor pixel area is reduced still further by metalization and
interconnect between pixels on th chip surface. This added overhead is
probably greater for smaller pixels putting them even deeper realtive to
Foveon. One might guess the diffusions in Foveon's chip are also thinner than
an on-chip filter, improving things further. In fact for the first layer
there should be little to no lateral effect. This means the sensitivity drop
off with lateral light rays is probably different for the three colors
leading to yet another variation in color sensitivity with extreme wide angle
lenses! This may be a negative for Foveon but given the chip should work with
much wider angle lenses to start with it is probably still much better.
Regards,
Tim Hughes
TimHughes@xxxxxxxx
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