[filmscanners] RE: Newish Digital Tech

["Austin Franklin" <austin@darkroom.com>]

Robert,

> Well, since the original poster was talking about photon noise I was only
> mentioning photon noise and for that my statement is true.

Yes, for photon (shot) noise, your statement is true.  I guess I read the
original poster’s statement differently, and the source of noise wasn’t
really defined.  The point I was trying to make, after understanding what
you added, was that for a CCD device, the noise floor is significant to the
SNR.

> Now
> you come and
> talk about floor noise.

Yes, because it related directly to the generalization that, and I quote the
original statement I was questioning:

“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.”

He gave no explanation of what the source for the noise was he was referring
to in the original post, as far as I could tell.  You and I figured that one
out as to what he must have been talking about.

And, given other sources for noise that are inherent in a typical CCD
system, that original statement did not look right to me, which is why I
asked for clarification.  Of course, as the numbers get larger, the  noise
floor becomes less significant, therefore making that generalization more
accurate.  And, the original poster did say “at high levels”, but it appears
those high levels aren’t achieved when using CCD devices due to the well
being full beforehand.

> As you argue your case I could argue that your
> numbers are wrong because you forgot other sources of noise, etc.


Forgot as in intentionally left them out, yes.  I believed (right or wrong)
the noise floor and the shot noise the two most significant sources of noise
in a CCD.  I haven’t calculated the significance of the other sources, but I
’d certainly like to know how significant they are...so at some point in
time I’ll do that.

> I agree
> that you can't look at photon noise only but I just was guessing
> about what
> the original poster was talking about.

Understood.  I was thinking beyond that in an overall sense to the original
statement, and applying that to an overall analysis of noise for a CCD
imaging sensor.

> But the point here is that
> no matter
> what anybody says you always turn things around so that it looks wrong

I don’t believe I told you that what you said was “wrong”.  I said I wasn’t
seeing the sqrt2 in the overall picture as being that accurate.  I was
combining what you said with noise floor (being I believe that is the only
other significant source of noise as it relates to this discussion) and
relating that to the overall picture (no pun intended).

> and
> what you say is right.

I don’t care one wit if what I say is right or wrong (despite what some may
believe), I was merely asking for explanations, and providing my
understanding, right or wrong.  This is a discussion and a discovery process
(at least for me), not a matter of who’s right or wrong.

I very much appreciate the information/analysis you (and of course others)
have provided.  And, just as a note, there are some mistakes in my
arithmetic in that post ;-)

Austin

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