The web site that I suggested people interested in this look at, which
was a 20 something page review of the new Sigma d9 with X3 chip camera,
has a page where they compared each color channel on the Sigma d9 and
the Canon EOS D60 camera. The results, to me, at least, clearly show
the Foveon chip as having much lower general noise, especially as light
levels drop /sensitivity/gain increases at ASA 400.
Again, the full article is at:
The comparisons of the one gray square in the MacBeth chart to a CCD
camera (a Canon EOS-D60) is on page 15 of the review.
(this link may not work, you may have to go to the earlier url and then
use the drop down menu to get to page 15)
Paul D. DeRocco wrote:
>>From: Austin Franklin
>>
>>Hum. Is that true? I don't know that I believe that. What, exactly, do
>>you mean by noise? Noise has MANY sources.
>>
>>I believe the more accurate the number of photons you capture, the more
>>accurate your information. Also, the more accurately you characterize the
>>loss, as well as the more repeatable it is, the more accurate your
>>information. It also depends on the accuracy of your sensor.
>>
>
> Of course there are other noise sources. But light, just light electricity,
> is a statistical process. At high light levels, as at high current levels,
> the number of photons or electrons is so large that the random fluctuations
> are a small percentage of the total. If you double the number of photons
> that you capture, the random variations only increase by the square root of
> two, improving the signal-to-noise by 3db. (Of course, other fixed noise
> sources, like electrical noise in the A/D amplifier, and quantizing noise in
> the A/D converter, provide a noise floor.) Conversely, if you halve the
> number of photons that you capture, the S/N degrades by 3db (as long as
> that's the dominant source of noise). This is true even if you count photons
> with 100% accuracy.
>
> This explains, for instance, why my 2MP Digital Elph has lower noise in low
> light than my 5MP DiMage 7. The pixels are larger, and capture more light.
> The full-frame CCDs in the high-end 35mm digicams are even quieter, because
> the pixels are bigger still.
>
>
>>But, let's use what you say...the Bayer pattern CCDs has only ONE
>>
> precision
>
>>color filter over each sensor...but the Foveon has up to THREE. One would
>>reason, that by your claim, that the Bayer pattern sensors have,
>>therefore, less noise. Right?
>>
>
> No. In a Bayer pattern chip, each site makes use of one third of the
> spectrum, and discards the other two thirds. In the Foveon chip, the other
> two thirds of the light is absorbed and measured in the other two layers.
> Another way of looking at it is that the Bayer pattern requires that each
> pixel be divided into three separate smaller sensors, one for each color
> (50% greeen, 25% red, 25% blue), and the smaller size of each sensor makes
> it capture less light.
>
> --
>
> Ciao, Paul D. DeRocco
> Paul mailto:pderocco@ix.netcom.com
>
>
>
>
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