Moose quoted my post :
>>
One issue mentioned is the fact that the readout speed becomes a problem for
CCD as the pixel
count gets large. TheCMOS devices can readout in parrallel reducing data rates
to the A/D etc if you
duplicate digitization. This keeps amplifier readout/digitization noise down as
bandwidth is then
greatly reduced.
>
And then went on to comment:
>>
Which is what Nik*n is doing with 4 separate data channels amplifiers
and 4 A/D converters in the D2X.
<<
There are actually a number of other advantages apart from the noise /bw/speed
tradeoff I mentioned. If the duplicate hardware is implemented right the gain,
and offset for each color channel can be set individually. In most cameras
there is only one amplifier for all three colors, before digitization occurs.
This means that the camera sets the gain for that (single) channel so that the
brightest color in the scene does not overload the A/D convertor. Effectively
this limits/reduces the measureable dynamic range and bit depth for the other
colors and hence can increase the digitization and other noise for those
channels. With seperate channels, dynamic range (offset and gain) is optimized
for each color. At first look this sounds like it would increase power, but in
reality the analog preprocessing can significantly reduce digital signal
processing requirements and the result is often a large decrease in power.
(Nucore has made a business out of this i.p.)
Regards,
Tim Hughes
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