Digital BW, The Print

> > If the range of the film stays fixed and the bit depth goes up the
> > width of the raw scan shouldn't change. If you decrease the bit depth
> > to less than the range of the film then the raw scan would get
> > narrower?
>
> Martin,
>
> I believe this is confusing because Austin has been trying for a long time
> to make dynamic range a function of bit depth

This is a fact. Please.  Bit depth IS a limiting factor of dynamic range in
the way current scanners are designed.

> and it just
> doesn't work that
> way.

Well, yes it does.  I'll bet you anything you want on it!  It does not HAVE
to work that way, bit it IS the way designers have chosen to design
scanners.

> Allow me to quote Andrew Rodney (digitaldog.com):
>
> "Dynamic range has nothing to do with bit depth!

He is right, and I have said this too, that you can REPRESENT any dynamic
range with two or more bits...but as I have said, that is NOT how scanners
happen to be designed.  And for a very good reason.  CCDs output an analog
signal that is (more or less) proportional to the light that the sensor
elements see...and when the light is twice as strong as the another light,
the signal has twice the strength!  AND that happens to pretty much coincide
with "integer density ratio values".  This is just REALLY simple.

> They are completely
> different spec\ufffds. You can have a scanner with 16 bits per color and a
> dynamic range of 3.3 and you can have a scanner with 12 bits and a dynamic
> range of 3.8. Bit depth is the number of steps. Dynamic range is
> the height
> of the star case. You can have a staircase that\ufffds 20 feet high and have 40
> steps. You can have a staircase that\ufffds 30 feet high and have 30 steps."

He is talking about theoretically, and I have stated this exact case too
time and time again, but is had nothing to do with the reality of how
scanners ARE designed and how they work.  A two bit scanner, though it could
REPRESENT a dynamic range of say, 4.0, could only give you line are!  You
would get NO tonality.

This is a typical thing that someone, first exploring how a scanner works,
brings up...as evidenced by countless explanations on the filmscanner news
group...  It is an EXCELLENT venue to discuss how scanners work, and
typically indicates that the person is understanding something...but this is
also a hurdle...and it seems you're hung up on this hurdle.

Wayne Fulton (www.scantips.com) and I had a very good discussion on this a
while ago, and he updated his web site based on some "issues" I had with his
explanation of this.  You might want to poke around there and read, I
believe it was tip 14...

> That's what the Minolta link that irked Austin was trying to
> establish.

That's why it's WRONG!

> 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).