Digital BW, The Print

> I was always of the assumption that the raw data was invariably
> contiguous,
> and therefore, the more it filled a histogram, the more tones you had to
> work with. So I assumed that the larger it's span across the histo the
> larger it's DR, ergo, the better the scan. Now I learn there is more than
> one way to represent the data, and while it may look different it will
> function essentially the same. IOW, one is no better than the other from a
> quality standpoint, is that right?

There is no difference in "quality" of data whether it's high bit or low bit
justified, it's the same data.

> If I adjust the setpoints of low bit justified data, to make it's
> histogram
> look like that of the same scan which was high bit justified,
> would the gaps
> appear in the same places as the high bit justified data, would the two
> files be the same at that point?

Technically, you could make them identical...but it's impractical to be able
to because you visually could not pick the exact points I doubt.

> I assume the Leaf is low bit justified, right? Are most?

No, I believe the Leaf is high bit justified.  I'm looking through the code
to see...but from looking at the 16 bit data on the Mac, it appears to be
high bit justified...  A B&W 16 bit scan occupied the range from 0 to
64...and if it was low bit justified, that would be a HUGE dynamic
range...if I had a 16 bit histogram with zoom etc., I would be able to tell
;-)

> Martin had sent me two raw files from the same image scanned on two
> different scanners. I don't remember if both scanners have the same bit
> depth though; lets assume they do. Before manipulations one's histogram
> seemed much narrower than the other, so I naturally assumed the scan with
> the wider histogram was the preferable scan. However, I casually expanded
> each one to look decent, not even trying to make them look exactly alike,
> and when I checked their histos after the adjustments I was
> surprised at how
> alike they looked. Should I now assume that one scanner probably just low
> bit justified the data, while the other high bit justified it's data?

That could very well be the cause.  Was one 4x narrower than the other, or
something like that?

> Was this the conclusion of the discussion you were having with mike
> yesterday, where, like you, I thought he was suggesting that scanners do
> something of an auto levels on the data, but he was referring to something
> else.

Yes.  He apparently did not mean that the setpoints (auto levels) were being
set...

> Was it that he meant he thought most scanners should high
> bit justify
> their data because it makes for a more full looking 8-bit histogram, which
> would better impress novices like myself?

Yes, apparently so ;-)