Re: Nikon D40 vs D40x ISO newbie question

On 2007-04-28 23:56:24 -0700, "Roger N. Clark (change username to rnclark)" <username@xxxxxxxxx> said:

C J Campbell wrote:
On 2007-04-28 21:38:20 -0700, "Roger N. Clark (change username to rnclark)" <username@xxxxxxxxx> said:

C J Campbell wrote:

Ken is making a few assumptions, one being that a smaller pixel does not gather as many photons and therefore it is likely to generate more noise. We see that in point and shoots, but it is an open question whether the much larger sensors in SLRs have even begun to approach that limit.

Yes, they have reached that limit. See Figure 6 at:
http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary

For all tested digital cameras, and by inference, similar performance
of other digital cameras, the signal-to-noise ratio digital cameras
achieve is photon noise limited for signals greater than a few tens
of photons. That means the noise is given by the square root of
the number of photons converted to electrons by each pixel.
Just like a bigger bucket collects more rain drops in a rain storm,
larger pixels collect more photons. Because digital cameras
have reached these fundamental limits, it lead to a host of
predictable properties, ranging from high ISO performance to
depth of field limitations.

Roger

The trouble with your charts (and this has always been the trouble with your charts) is that they do not seem to have anything to do with actual results.

Actually they do. Some examples, Noise levels are just as predicted:

http://www.clarkvision.com/imagedetail/does.pixel.size.matter2

http://www.clarkvision.com/photoinfo/dof_myth

Theory is great, so long as it can predict results.

This is not theory; it is measured results with models that
are pretty standard in the electronics industry. Further,
the data I present is a compilation of my own analyses,
those of others and sensor manufacturers from their data
sheets. They are all consistent and all doing quite well
in predicting results. In astronomy the measured parameters
and models predict nicely what one gets in difficult conditions
in astrophotography. Then, DSLRs using these models are doing
photometry, and quite well.

According to your charts the Canon 1D Mark III should produce worse pictures than the EOS 350D or even the Nikon D70. This is demonstrably untrue.

Where do you get that idea? The 1D Mark III is not on the charts.
Canon states the photo sites collect the same number of photons as
the 1D Mark II (closer pixel pitch but better micro lenses), so
the 1D Mark III should plot at 7.4 microns on a line horizontal
to the 1D Mark II. That puts it still performing better
than a 350D or a D70.

I cannot tell you what is wrong with your charts. But it is obvious that there is something seriously wrong with them.

Perhaps you are mis-interpreting something?
If you can be more specific, perhaps I can clarify it, or perhaps
I will see an error (again noting some of the data on the
charts are from sensor manufacturers data sheets).

rOGER

It appears that your charts are an argument that more photons reduces picture quality and that there is nothing you can do about it. Yet here you claim that better micro lenses can correct the problem.

So, either the limit on sensor size has been reached as you said, or it can be increased further with better micro lenses or other engineering solutions, which you also said. It seems to me to be a contradiction, so please understand if a simple tax accountant seems confused.
--
Waddling Eagle
World Famous Flight Instructor

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