Digital BW, The Print

> Before going into the details, let me say that
> I'm always referring to a scale as it relates to human
> perception.

But not all sensors sense in "human perception" units...so I believe that is
going to cause some confusion.

> >
> > > The basic fallacy is the mixing of linear scales and exponential
> > > (or geometric)
> > > scales
> >
> > Er, I didn't mix them anywhere...but you're right, that would be a
> > fallacy...
> My main point goes back to using the "scale" (expon or linear) as
> defined by the human not by the measuring device.

I don't see how that matters.  Scale can be applied to either equally as
correctly.

> > > You are
> > > looking at the DynRange formula and seeing the term
> (maxpower/minpower)
> > > and "feeling"  that its the same thing as the ruler.
> >
> > The example of a ruler is fine, providing you understand what
> it means.  In
> > the example I've cited above using 6V/.01V, no matter where you
> are on the
> > scale, you can only measure to .01V.
>
> Seems like there isn't human factor here, saying you can measure 0.01V,
> sounds like everything is linear.

That doesn't matter, as it relates to dynamic range...which is what this
conversation is about.  The next paragraph (which I clipped) showed an
example using power.  Ruler works for either linear or logarithmic it doesn'
t matter...

> > Just as an aside note, in audio, just because you have doubled power,
you do
> > NOT get double the "loudness".  That takes ~10x to double the loudness.
>
> I'm really
> only interested in saying power is exponential, and I'll stick to
> using "loudness"
> just as a descriptive term.

Yes, but the "scale" watts is different than the "scale" that loudness and
you can't interchange the two in a linear fashion...

> For the last couple of paragraphs, I think you agree that "power" in the
> audio sense is an exponential scale.  It looks like you are also
> maintaining
> that  (maxpower/minpower)  has a "how many steps" meaning.
> This, to me, is the crucial point in this whole discussion.  Its a purely
> mathematical issue that for an exponential scale, the max/min ratio
> is just a size of the total range.  There's no meaning of step here.
> I thought my different of exponential series in the last post clearly
> demonstated that.

It did not.  You can determine the dynamic range of ANYTHING that has a
largest absolute signal, and a smallest discernable signal, even if that is
in dB!

Sound pressure level meter spec: Range: 20-120dB, noise: 2dB.

Dynamic range 10log10(100/2) or 17dB, which is the same as 10**1.7, or 50...

> > BUT if you are measuring in "loudness", well, then, you can't
> very well give
> > "watts" as your unit, as watts is NOT the same relative measurement of
> > "loudness".  I believe that is a clear mistake.
> You can use watts its just that you have to think in exponential series.
> This is the point with the various series that I wrote earlier.

Sure, you can use watts, and sure you can use loudness...but you can't mix
the two.  They are different scales.

> >
> > <big snip>
> >
> > > See now have:
> > > DyR  = maxdb - mindb
> >
> > Sure, note both are in dB.  Nothing wrong with that.
> My point here was to mathematically change equation and show
> it no longer has the divide that (at least I'm surmising) makes the
> original form of equation look like "number of steps".

Well, perhaps I misunderstood what you were trying to get at, then I'll have
to say that your equation is wrong...if you are using an example like I used
with the sound pressure level spec...the dynamic range of that device IS NOT
100 - 2, it is as I stated it.

>   BUT...if you are
> > trying to claim somehow that has something to do with density
> range, it does
> > not!  Density measurements are NOT in dB, period.
> Well, yes, density and dB are different.  But I'm glad you noticed the
> hint of them having some parallelism.

NOTICED THE HINT?  I've said this all along, and known it long before
conversing with you about that.  Thanks, but I didn't need a "hint".

> Mathematically they sure do
> look a lot alike, don't they?

Yeah, but that isn't relevant for anything as far as our discussion goes.

> I'd sure like an awful good reason to think all this parallelism
> should be ignored.  If you have a reason, please do tell.

Because it isn't relevant in this case.  A lot of things are in log, but
they aren't related.

> > to the meaning, or why even bother adding it...especially considering
> > dynamic means "characterized by continuous change".  That hardly seems
>
> Well, at least we both have cute quotes now :).   I'm going to
> have to keep
> asking what's "continuously changing".

Well, if you understood the concept of dynamic range, then it would be
obvious ;-)

> > applicable to two static numbers!
> Aren't your maxpower and minpower measurements basically a
> "static" numbers.

Er, maxpower and minpower are YOUR numbers, not mine...

> What are you calling "continuous change"?   I don't see any "continuous
> change" when you measure the power amp and a certainly do see any
> continuous change when you get to the photo print.

If your measurements are 100 watts with a noise of 1 watt, then the amount
of change you can discern is 1 watt...any CHANGE must be 1 watt or greater
for you to perceive it.

> > > Dynamic range is a range just like any other range,  the word
> "dynamic"
> > > is just a qualifier that says "perceptually interesting part of".
> >
> > I don't mean to be snide, but that's just silly.  So many
> things have ranges
> > specified, and they aren't called "dynamic ranges",
> I didn't say all  ranges are dynamic.  I said a "dynamic range"
> is firstmost
> a range and it ought to AT LEAST have the notion of being a range.
> The "dynamic" is an ADDITIONAL modifier, qualifying additional limits.

I believe the intention of "dynamic range" is dynamics OF THE range.  I do
not know the history of the term, but perhaps that may be enlightening.

>    Well it seems that if we're defining DynRange of
> something whose key property is density, we ought to end of with some kind
> of range whose units are density.

Well, no.  Dynamic range is ALWAYS in dB, not density.  When you measure the
dynamic range of a audio equipment, you don't get volts, you bet dB.  That
is probably a MAIN source of your confusion.  dB IS dB, and is purely a
relative value, and has no unit BUT dB.

> Similarly you could be talking about the DynRange of a natural
> scene --  density wouldn't be to useful since there isn't any.

How's that?  Scenes absolutely have density.  If you can measure density on
a print, what's to say the print isn't the scene?

> Here
> you ought to use whatever units you can measure.  (My spotmeter does
> EV at ISO 100 for instance, so I'd be thinking of DynRange in EV's).

If you measure the dynamic range of your EV meter, say it has an overall
range of 20 EV, and is good to .1 EV, then it's dynamic range is
10log10(20/.1) or 23dB, NOT 23EV.

EVERY dynamic range equation shown has the result in dB.

Regards,

Austin