Digital BW, The Print

> > This is a fact. Please.  Bit depth IS a limiting factor of
> dynamic range in
> > the way current scanners are designed.
>
> Austin, here you are saying one thing, below you say another. Ill point
> it out later.

I didn't see you point this out anywhere in your post here...  I just don't
understand why we're discussing this, it's just a plain fact when
representing INTEGER DENSITY RATIO VALUES (which is how scanners work), the
number of bits are the limiting factor of the dynamic range.  If you are
representing some other "values", then the number of bits may or may not be
the limiting factor.

> Here it is.
> In this case (and many less extreme ones) how is bit depth the limiting
> factor?
>
> All scanners used to be only 8bit, but they still captured film with
> the same d-range that the film we scan today has.

Show me one example of a scanner that used 8 bits, and captured a dynamic
range of 3.2 or greater.  They may have RETURNED 8 bits of data, after the
setpoints and curves were done in the scanner driver...but the actual A/D
output was much higher.

> > > Bit
> > > depth is how many tones are used within the dynamic range,
> not how many
> > > tones it takes to give you dynamic range.
> >
> > No, that isn't how scanners are designed.  Bit depth does
> nothing but expand
> > the tonal capture ability into the dark regions...it does NOT give more
> > tones within the same dynamic range...for the same image
> (unless the image
> > is clipping).
>
> It does if you are talking about the old scanners vs the new.

Show me an "old" scanner that does as you claim.

> There is
> no reason to limit ourselves by saying todays scanners give us more
> than we could ever use. Film is analog, scanner makers should come out
> with a scanner that captures the full 16bits with a density range of
> todays 14bit scanners. Which would entail differentiating more tones
> rather than the ability to capture a more dense negative.

That is not necessarily true.  Because it's analog, doesn't mean it's
infinite.  You're forgetting a little thing called noise.  Noise will limit
the number of tones you can get.

> I am not
> saying it is possible, but I would think someone would be able to
> figure it out.   Nobody has yet because it hasn't been necessary...

It IS possible, I've already "figured it out", but, as you say, it just
isn't necessary.  It's actually very simple.  The data out of the A/D does
not represent integer density ratio values, but fractional density ratio
values.

> I have taken issue with the term dynamic range. Scanner companies use
> it to mean their scanners capture more information.

The term "dynamic range" has been around long before scanners, and has a
fixed meaning in the engineering community.  Because it is
misrepresented/misunderstood by some does not change the definition of it.

> If a
> scanner could really capture 4.5 density-range in a 12 bit space,

As I've said, you CAN capture (if you design a scanner to do so) any density
range into 2 or more bits...BUT...the values you get are NOT integer density
ratio values.

> then
> a normal negative's range would have to fit into a much smaller space
> than 12 bits.

For that particular scanner, IF that scanner was designed to operate that
way, that could be true.  Perhaps the scanner could expand the data to fit
the entire 12 bits.

> Which would mean that, with that negative, that scanner
> would actually capture less information than a 3.3 d-range, 12 bit,
> scanner.  Does this make sense?

Only if the scanner was designed to operate that way.

> That is one of the reasons I think they should have called it density
> range. And left the term dynamic range to something more along the
> lines of bit depth.

But they are both the exact same thing.  Density is a ratio, just like
dynamic range is.