How does the D3 achieve such high ISO?

Started Feb 17, 2008 | Discussions thread
ohyva Veteran Member • Posts: 6,342
Re: The mathematician's vs. the engineer's approach

Marianne Oelund wrote:

ohyva wrote:

ejmartin wrote:

Really? Googling "dark current noise", the first listing
http://www.roperscientific.de/tdark.html

I just wonder why then so many research activities in silicon sensor
structures to minimize the dark current. Like this one WO patent
http://www.wipo.int/pctdb/en/wo.jsp?wo=2005083791

Any isolation should not make any effect to thermal noise as far as I
can remember to my very much past phisics lessons.

I can assure you that the dislocations which that patent addresses
are without question of thermal origin. Do you honestly believe that
component of dark current would persist at absolute zero?

Absolute zero point - no as there is (in theory) no movement whatsoever.

Is this strictly proportional to temperature - I do not know, as I do no longer remember all the mechanisms and formulas related to different current/charge leakages.

Term "thermal noise" AFIAK and can remember has a special meaning in physics, so not all thermal dependent phenomena fall in this category.

To the main point of this post:

Mathematicians expend considerable effort studying single-point
anomalies such as singularities, path-dependent limits, etc., which
have no practical real-world counterpart (aside from black holes).
Engineers recognize what is most significant, pertinent and
practical, and limit their dealings to such aspects.
What you are doing is devoting a disproportionate effort to effects
which, if significant, would already have been included in the noise
models.

And engineers, in real life, fall regularly into problems when trying to oversimplify the models. I can assure I know and have learned this in a painfull way in my 20 years of professional work in electrical engineering.

The models work very well, to experimental accuracy. That
has been repeatedly demonstrated, and if you insist on pursuing
negligible effects, assume that you will be on your own with them;
you can certainly count on no support here.

So did the Newton Laws before Treory or Relativity was introduced, now recently challenged with theories of Quantum Physics. All these in the dómains and limitations they have.

Finally, it is beyond annoying to have one who has asked a question,
then turn around and put up a series of arguments against the answer
provided. Emil has been more than patient with you - far more than
you deserve.

Patience is a virtue.

And Marianne, when you make the sort of statement below, I guess we can expect you have many the analysis beyond any reasonable doubt. So complaining other people to be too strict in details is a bit indiscreet IMHO.

"Fact #1: Quantum efficiency is significantly higher on the D3, yielding greatly reduced shot noise.

Fact #2: Read noise levels are nearly the same on the two cameras, across the ISO range.

Fact #3: The D3 has in-camera NR which significantly improves IQ of its JPEG output. "

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