Roy,
> > > What's wrong
> > > with going from
> > > 1:1 to 1.01:1 to 1.02:1 ...
> >
> > Because noise is 1, and you can only measure in increments of
> noise. In a
> > system that has noise of, say, 1V, you certainly can't measure
> 1.01V, now
> > can you?
>
> You probably haven't seen the post yet. But, I've actually demonstrated
> that you can
I'll have to read what you wrote up, but I KNOW that it simply is not
possible when noise is the limiting factor of dynamic range. It's just
simply physically impossible to do what you are suggesting, that's not how
dynamic range works. You can ONLY measure down to the level of noise. If
you measure 1V in a system with 1 volt noise, your 1V measurement gives you
a range of .5V to 1.5V. You can NOT measure 1.01 volts with 1V of noise.
The reading is simply not possible to get.
> I really wish you'd read what I write and not snip out of context.
> Immediately after the above paragraph I wrote:
>
> Fine, but the trouble is: scanners don't work anywhere even remotely
> close to that scenario. This is what scanners actually output
> as the levels:
Yes, I read all that, but that doesn't negate my comment, now does it? My
point of snipping that was it was irrelevant.
> >> Austin, don't take my word or the web's word for it. Try it yourself.
> >
> > Roy, I've designed film scanners, and have been designing
> digital imaging
> > systems for over 20 years. I KNOW how they work.
>
> You may know scanners inside and out. But with scanners, resolution
> and levels are all based on QUANTIZATION noise or more accurately
> QUANTIZATION ERROR. You may pick this quantization based on the real
> random noise of the system, but all the properties about resolution and
> number of levels are based on the properties of quantization.
I'm getting the feeling you don't quite get what quantization error is.
Here is, what appears to be, a very good write-up on digitizing,
quantization error, resolution etc. Most everything we've been discussing:
You select your A/D resolution such that the quantization error is matched
to the noise in the signal you are trying to digitize. It's a fact that the
dynamic range of the input signal to the A/D has NOTHING to do with
quantization error. If you have too few bits to digitize the signal, the
quantization error of your DATA is high. You always have a 1/2 lsb
quantization error...just like in analog, +- noise.
> The true random noise of the input signal has VERY DIFFERENT properties.
Would you describe what properties you are talking about?
> Quantization noise is a hard limit on resolution,
Yes, the NUMBER OF BITS limits the resolution. Exactly what I've been
saying for ever...
> but RANDOM noise
> presents no such boundary on resolution.
You are claiming that you can resolve to less than noise in the case of a
CCD? Well, then why does EVERY dynamic range equation dealing with
digitizing CCD data show noise as the MDS and base the number of bits
SPRCIFICALLY on dynamic range?
> With multiple samples
> that are averaged you can increase your resolution accuracy.
Multiple samples does NOT increase your resolution, it only helps decrease
noise IN the signal you are digitizing. Yes, in SOME circumstances you can
possibly do some processing to decrease noise, but not really in the case of
the film scanner. Anyway, so what? That's really superfluous to the real
discussion...another minutial tangent...IMO.
This really amazes me at how many things you guys can attempt to throw into
something that's just so simple...
Austin
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