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Re: filmscanners: Sprintscan 120 and new negative proile scheme



From: Tony Sleep <TonySleep@halftone.co.uk>


> On Mon, 11 Jun 2001 18:45:13 -0400  Dave King
(kingphoto@mindspring.com)
> wrote:
>
> > Sorry Tony, but I don't agree with this.  Neg films vary primarily
in
> > the mask layer.
>
> But that seems to be a variable, since mask density appears to vary
> according to processing.
>
> > Processing is standardized by manufacturers, and good
> > labs use the same technology to insure consistency with C-41 as
they
> > do with E-6.  In my experience, neg film of one type is as
consistent
> > as chrome film.  If you shoot under controlled conditions in the
> > studio and use a good lab for processing, you'll see this when you
get
> > to the darkroom.  Exposure is another story, but the manufacturer
or
> > lab can't be faulted for that.  But even here color negs vary less
> > than chrome films.
>
> It's true I don't see a lot of variation in C41 films of the same
type,
> but it's not the film which varies, it's the image. The scanning
task is
> quite different from scanning slide. With slide, you have a fixed
> reference, with neg it's interpretive.
>
> The source of difficulty here is the latitude of C41 and ability to
> produce uncorrected results across a wide range of colour
temperature and
> exposure which you sort out later. With slide, you have next to no
> tolerance. If it's screwed on the film, you aren't going to be able
to do
> a great deal with the scan as the wide OD range occupies all, or
nearly
> all, of the dynamic range of the scan.
>
> If you always shoot colneg under more or less controlled conditions,
and
> place exposure on the same part of the curve (conditions more or
less
> imposed by slide) then, yes, I would believe profiling could be done
with
> reasonable precision - given a consistent lab.

That was my point.  I mentioned shooting in the studio, but outdoors
in sunlight should be about the same.

> But the utility of colneg is the amazing ~10stop range, which
enables
> exposure to be located however you want on the curve, and allows
enormous
> liberties to be taken with illuminant colour, including mixed
sources.

True, and I'm sure most of us take advantage of that range sometime or
the other, and goddam grateful for it too:).  But if one had an
accurate colneg profile, I would think one could get as good first
results with varying negs scanning as in the darkroom.  Can't really
blame a profile for not predicting light temp etc variables.

> In this scenario, the colneg is only a waypoint on route to the
final
> image which exists nowhere except in your head. You absolutely don't
want
> a mechanical, invariant translation as you would with
slide+profiles. It
> will look horrible, say, to get a 'straight' scan of an image taken
under
> flourescent without filtration.

But a 'profile' scan of the flourescent green chrome would have the
same problem.  It's going to come up looking pretty much like the
chrome, for better or worse.  You're still stuck doing alot of work.
Profiling isn't intended to deal with variables, it's intended to
establish predictible accurate results under standard conditions.  So
I *do* want an invarient translation for most work, and perhaps even
as a point of departure in editing difficult material, or at the very
least as a frame of reference.  If it really works accurately, time is
saved!

Canned neg profiles may be generally less accurate than dynamic
profiles (?), and part of the perception that neg profiles are useless
may come from this.  Practical color management is still so new that I
can imagine a few other reasons why neg profiles might seem useless
most of the time.

> You have a lot of freedom to muck about with values, as most images
leave
> plenty of headroom once scanned.
>
> DH's suggestion of a ring-around of profiles seems like it maybe a
handy
> shortcut from the info locked up in the neg to an image which
approximates
> what you were after, at least part of the way - by mapping response
for
> film under a variety of conditions.
>
> To restate St Ansel for the C21st 'The negative is the score, the
print is
> the performance, and profiles are pianola rolls' :)

And profiteroles served after the performance.  :)

> I'm sure you know all this stuff anyhow, and do it anyhow ('I am the
> colour management' :-) All I'd add is : isn't it curious how much
colour
> correction can vary from one neg to the next, even when taken in the
same
> place and same time.

Hummm, can't say I've noticed color variations of this sort, in the
darkroom or on the desktop.  Maybe later.  :)

Dave





 




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