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Re: filmscanners: Sprintscan 120 and new negative proile scheme



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.

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. 

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.

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' :)

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.

Regards 

Tony Sleep
http://www.halftone.co.uk - Online portfolio & exhibit; + film scanner 
info & comparisons




 




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