[filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!

["Austin Franklin" <darkroom@ix.netcom.com>]

> > -------direct quote from Proposed ISO standard-------------------
> >
> > 7.2 Scanner dynamic range
> >
> > The dynamic range is calculated from the Scanner OECF by:
> >
> > DR = Dmax - Dmin                (7.2)
> >
> > DR = Scanner Dynamic Range
> > Dmax = Density where the Signal to noise ratio is 1
> > Dmin = Minimum density where the output signal of the luminance OECF
> > appears to be unclipped
> >
> > -------end quote from Proposed ISO standard-------------------
> >
> > (and OECF is opto-electronic conversion function)
> >
> > You will notice, it is exactly as I have described it, a RANGE.
>
> I do not see ANYWHERE where it says dynamic range is "a" range.  It shows
> the RESULT of a calculation WITHIN A RANGE (Dmax), divided by the noise
> (Dmin), but the result is NOT "a" range.

Sorry, in my haste to get out of the house, I transposed Dmax and DMin in
this post...obviously, as defined above, Dmax is the noise level, and Dmin
is the "overall range".

> Very easily.  One of the terms (Dmin) is the noise, as CLEARLY stated

Should be Dmax...

> (Signal to Noise Ratio = 1...which means the noise equals the signal), and
> the minimum increment of measurability in a system IS noise...and
> therefore,
> you can only measure so many points within the overall range and consider
> them discrete points.
>
> The other term (Dmax) is simply the overall amplitude the signal can
reach,
> which is based on zero being the low bound, and Dmax as being the high
> bound.  If you divide the overall amplitude by noise, that gives you the
> resolution within that overall range with which you can discern.

Here too...

> I have ALWAYS contradicted what you're saying.  You CLEARLY mistakenly
> believe "dynamic range" is "a" range, and it is clearly not.  A range
> requires two bounding terms (or one with the other being considered 0, or
> simply the overall range, as in the amplitude), and dynamic range, as per
> the equation you have provided, shows that it is a number, that is in dB,
> that is derived from the information available WITHIN a particular range
> (DMax is the overall range), and that does not make it "A" range.

and here too...

Sorry about that.

Austin

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