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Old Aug 28, 2003, 9:21 PM   #21
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Vox-

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You mentioned at least 2 variables contributing to sensitivity, but are you excluding effective area? Since this is something that
may be more easily scaled with current sensors and better manufacturing yields? Or are you saying there is more mileage in
developing the physics of sensor design and keeping the area small. VOX
I didn't mean to explicitly exclude effective area, but rather I was (over) simplifying the problem. If the only noise source in the system was from thermal agitation and background radiation at the detector site, then the noise effects would scale with detector site area just as the photon charge scales with area.

I agree with your reasoning though, Vox, if you also include other real noise sources outside of the photo detector itself, such as amplifier noise and jitter induced noise artifacts in the readout chain. These noise sources are pretty much constant for a given disign and don't scale with detector area.

Therefore, there is some crossover point where noise from amplifier/readout/A-D converter start to dominate the noise captured in the detector itself and thus tend to dominate the system noise component. When this crossovr point is exceeded, then the larger the effective photo sensitive area is, the more signal there is relative to the total system noise, even though the larger area also brings the absolute noise level up.

As to whether there is more lift from advances in sensor physics or semiconductor processing techniques, it's hard to say. Just about the time you make some broad generalization that says this is as far as one can go with silicon, some physisist will come up with new dopants which throws the whole thing up for grabs again. Perhaps the consumer camera world will see other (more exotic) materials used in their detectors when/if the volume is sufficent to drive the prices down.

Let's not lose sight of the fact that all of this stimulating discussion started out asking for a comparison of digital sensor sensitivity compared to film. And I still maintain that with today's commercial film and sensor technology, that film is more sensitive.
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Old Aug 28, 2003, 9:32 PM   #22
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Originally Posted by jawz
Let's not lose sight of the fact that all of this stimulating discussion started out asking for a comparison of digital sensor sensitivity compared to film. And I still maintain that with today's commercial film and sensor technology, that film is more sensitive.
Well, conventional cameras to digital cameras anyway...it was never qualified to the type of film.
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Old Aug 28, 2003, 9:48 PM   #23
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>> .. all of this stimulating discussion started out asking for
>> a comparison of digital sensor sensitivity compared to film.


Did it?

> Well, conventional cameras to digital cameras anyway...

My first impression was that it might be asking about
mechanical sensitivity of digital vs conventional cameras.
Now we'll probably never know, until we all drop-test
our cameras.

The most "sensitive" photography in terms of low-light
is probably astronomical (telescope) work. Didn't "digital"
(CCD) replace silver-halide in that role decades ago?

The answer to both questions is probably "yes, but".
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