View Single Post
  #76  
Old July 8th 07, 10:54 PM posted to rec.photo.digital.slr-systems
Roger N. Clark (change username to rnclark)
external usenet poster
 
Posts: 1,818
Default One upmanship and Canon's claim

Alan Browne wrote:
Roger N. Clark (change username to rnclark) wrote:
Alan Browne wrote:

(and our cameras will be imaging spectrometers too). Oh, and make
read and thermal noise zero.


Boltzman says no-can-do. You could always add heat removal but it's
unlikely that you can cool an entire portable camera sensor to
milli-K levels.



It need not violate any physics,


I didn't say "violate" just that you need very low temps...

and I should have said
effectively zero, not absolutely. Read noise in the
best consumer cameras is already under 4 electrons
at room temperature and reports are reportedly even lower
in the 1D Mark III. With more accurate 18-bit converters
and on-pixel electronics, 1 electron read noise is possible.


I was under the impression that absent very cold temps, that noise
(thermal at least) is simply unavoidable. If 18 bits/channel is
achieved and you throw away a couple/3 bits per channel for noise, then
whatever is left should be quite clean indeed.


The noise is dependent on temperature, as well as capacitance
and resistance. So instead of reducing temperature, for
example, one could reduce one of the other parameters
that determine noise. A good explanation with
equations is he

Concepts in Digital Imaging Technology
CCD Noise Sources and Signal-to-Noise Ratio
http://learn.hamamatsu.com/articles/ccdsnr.html

(Hamamatsu is a sensor manufacturer.)

Of course none of this is easy, as designs are quite mature.
But that doesn't mean a new design won't come along that
improves things. But since most images have noise dominated
by photon noise, most people will see little difference.
The main performance factors in digital cameras a
pixel size, quantum efficiency (pretty much the same across
current digital cameras). So we are down to pixel size as the
major factor in performance at present. Of course the camera
manufacturers don't want you to hear that. ;-)

Roger