Re: CMOS vs. CCD -- Link to Article


"Phil Wheeler" <w6tuh-ng7@xxxxxxxxx> wrote in message
news:ikjkf.686$hI1.517@xxxxxxxxxxxxxxxxxxxxxxx
> Chris L Peterson wrote:
>> On Sat, 03 Dec 2005 07:03:34 GMT, "David Nakamoto"
>> <res07oeg@xxxxxxxxxxx> wrote:
>>
>>
>>>If they can beat the noise down to CCD levels, keep the sensitivity and
>>>dynamic range, and deliver more pixels, then it would be something.
>>
>>
>> There is a lot of misunderstanding about CMOS. It isn't necessarily
>> noisier.
>
> Indeed. My Canon EOS 20D has a CMOS imager and has very low noise at
> relatively high ISO values (800 & 1600 are very usable).
>
> Phil
Though this is somewhat 'misleading', since the reason the Canon cameras
give this performance is partially the internal processing they perform.
The chips contain a factory 'noise map', effectively a bias frame, and
data on the rate the noise grows with time for each pixel, and if asked
not to perform an 'auto-dark' (some models if asked to do long exposures
will perform an automatic dark subtraction), will instead synthesise a
'dark' from these numbers, and subtract it. The result is that the dynamic
range of the image decreases with longer exposures, and this can be
measured and verified. There has been quite a lot of discussion on various
groups about just how much processing these cameras do. They perform very
well indeed in general, but the noise is not as low as it seems....

Best Wishes


.

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