[filmscanners] RE: 8 bit versus 16

["Austin Franklin" <austin@darkroom.com>]

Hi Laurie,

> >But...here's the rub.  If you get the setpoints and tonal corrections
> >reasonably close in the scanner driver, keep in mind, this is all done
> using
> >high bit data...  it's just how scanners work...it completely moots the
> >discussion of 16 vs 8 bit files...as there would be no need to do large
> >tonal moves post scanning.
>
> The other shoe?
>
> First, it assumes that the software being used allows for this;

Yes, I understand that...and have been told that some software doesn't have
decent tools, like a decent setpoint tool, and a decent curve tool, and a
histogram display...

> but granting
> that it does for purposes of argument, it may completely moot the
> discussion
> for you but not for others for a number of reasons that they are trying to
> tell you but while you are listening you are not hearing.

I think you're mistaken about that.  The discussion is about 8 bit vs 16 bit
files and tonal manipulations.  The ONLY thing I am challenging is the need
to do high bit tonal manipulations to color image files, period...nothing
more, nothing less.

> Among
> those is the
> fact that since as you say if you get the setpoints and tonal corrections
> reasonably close to the scanner driver using high bit, you have done
> essentially what they say they are doing just they have choose to do the
> setpoint correction and tonal adjustments to the high bit data in a third
> party editor rather than in the scanner...

The only point of my mentioning that the scanner uses high bit data to do
that was simply to mention it.  But there is another reason that scanner
hardware uses more bits, and it has not a single thing to do with tonal
manipulation ability.  It is density range.  When you scan, your image only
takes up some "part" of the overall N bits.  That "part" is larger for
slides, as they have a higher density range, and lower for negatives.

> ...even if it is possible with the
> scanner software that they are using since they feel more
> comfortable with
> the third party image editor or it is better than that of the scanner
> software.

Not something I have any issue with.

> I think they all recognize that to apply some Photoshop plugins
> and features or even to print they need to convert the file to 24 bit in
> order to do so and that that should take place after the tonal corrections
> and setpoionts have been established.

Setpoints, yes...but tonal corrections can take place in 8 bit color space
with no visible degradation over high bit space.  At least in the hundreds
of images I tried this with...and that's not to say there isn't an image
that may benefit from high bit manipulations, but I've yet to see it...and
no one's able to produce it ;-)

> There is also the fact that, while
> one can establish set points and tonal curves that match the optimum
> hardware capabilities of the given scanner and that these can remain
> constant...

But you don't set setpoints and tonal curves to match the scanner, at least
I don't...nor should anyone, really.  You set them to match the image.  The
images can vary greatly, depending on the film, exposure etc.

> ...for most of us, the subject matter being scanned does not remain
> constant and may require modification of the set points and tonal curves
> from scan to scan or so and is dependent on the original being scanned
> rather than the devices capabilities per se.

I've never said any differently, and that is how I scan as well.

> Such modifications
> may best be
> done after the scan in an image editor where one can actually preview the
> consequences of proposed adjustments on the fly in real time as they are
> being done.

Hum...my scanner software does exactly that...  But, this is really not the
issue at hand.  The issue at hand is only tonal curve manipulation in 8 bit
vs 16 bit...not setpoints.  Setpoints MUST be done to high bit data, and
I've never said any differently.

> In that case the establishment of setpoints and tonal curves
> for the scan should be taken as merely a preliminary raw approximation
> rather than the final product with the main tonal moves being done post
> scanning.

Even if you could get high bit data from a setpointed and tonal curved scan
(which in my experience most scanners either give you
non-setpointed/non-tonal curved high bit data, or setpointed and tonal
curved 8 bit data), I still contend that tonal curve manipulation won't be
any better because you do it with high bit data.

> Second, it very well can be the case that one does not wish to
> replicate the
> exact setpoints and tonal curve of the original that was scanned but to
> deliberately alter or modify the tonal character of the scanned result for
> artistic or other reasons; there would be every reason for doing major
> tonal moves post scanning.

OK...but again, the contention was only tonal curves, not setpoints.  But,
setpoints aren't really an issue either.  Yes, they must be initially
applied to high bit data and MUST be simply because that is how scanners are
designed, but the setpoints should contain all the valid image data, and
therefore allow for anything you mention to be able to be done after the
fact...and therefore only need to be set once.  They are far more
deterministic than tonal curves.

Regards,

Austin

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