RE: SilverFast (negafix)

[Scott Robertson <scott.robertson@xxxxxxxxxxxxxxx>]

As I understand the Negafix process, the algorithm does more than just
orange mask removal and reversal.  A library of characteristic curves (which
describe how the CMY dye layers respond to increasing exposure to light) for
various film brands and emulsions is supplied.  Since each emulsion has a
unique characteristic curve (some may have a longer toe or shoulder, showing
more compression of shadows or highlights, some may have steeper straight
line portions, showing more contrast, some may have a warmer or cooler or
more neutral response), one must take these curves into account when
inverting the image after the orange mask has been removed in order to more
accurately reproduce the correct color balance and contrast of the image.  A
problem I've had with Negafix, however, is that the supplied curves for some
of the film I am scanning, namely Kodak Supra 400, show way too much
contrast and highlight compression.  In other words, the straight line
portion of the Supra 400 Negafix curves is too steep and has a very long
shoulder.  Scanning frames shot of snowy scenes with these curves resulted
in very contrasty images with blown-out highlights and no highlight detail
at all.  In fact, none of the supplied curves have produced perfect results
for me if matched up with the correct film emulsion.

You can, however, adjust these curves and save them, which is what I did for
my Supra 400 negatives.  I actually discovered that the curves supplied for
Kodak Gold films were a much better match for my Supra negatives, so I used
them as a basis for creating my own set of curves for the Supra 400 stock.
It was also simple to create a selection of color-corrected curves to
correct for things like warm tungsten lighting vs. cooler daylight by
scanning frames of a Macbeth Color Checker chart taken under these lighting
conditions and correcting for tone and gray balance.

Scott Robertson


-----Original Message-----
From: Paul D. DeRocco [mailto:pderocco@ix.netcom.com] 
Sent: Tuesday, March 12, 2002 12:25 AM
To: scan@leben.com
Subject: RE: SilverFast (negafix)


Another bitch about SilverFast prior to Negafix: the manual showed a
drop-down list of different negative film types, but the LS-2000 version of
the software didn't provide such a selection. Their explanation was that the
LS-2000 does negative to positive conversion internally, and there's no way
to adjust it for different film types. When I asked why they didn't simply
run the scanner in positive mode, and do the reversal in their software, I
got no answer.

The explanation of NegaFix suuggests that it reads the color of the mask by
looking at the borders around the picture, and compensates automatically.
Now that it does that, I can't understand why you have to specify the film
type in greater detail than before. Or conversely, if you can specify the
film type down to the specific brand, what does one need NegaFix for?

I've chosen not to upgrade to 5.5 because a) I fear that the full advertised
negative processing (perhaps even NegaFix) is still disabled in the LS-2000
version, b) I don't believe they've fixed the fatal flaws that the old
version had, and c) I feel the first few hundred bucks I spent were a
ripoff, and I'd feel like a complete shmuck if the added $45 turned out to
be a waste, too. Until someone tells me they've rewritten the program from
the ground up, and fixed these issues, I'll not upgrade, and continue to use
NikonScan.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

> From: Harry Minoru Shin
>
> 1.  from what i can tell and from the silverfast / lasersoft website 
> states, negafix is ONLY on version 5.5, and thus whatever you have on 
> 5.2 is not negafix. 2.  i can't recall in detail what version 5.0 was 
> like, but i believe negafix will differ from you have in the following 
> respects:  a)  in the older versions, when you choose "negative", a 
> little dialoug box pops up and then you can choose very basic data 
> such as ASA, major film
> types (kodak, fuji etc...).   with negafix, you still choose ASA, the
> film company (kodak, fuji, agfa etc...) but it also has a huge list of 
> specific film brands (kodak royal gold, kodak gold, fuji reala 
> etc...).  and i assume via that huge list, the software algorhythm is 
> much more complex, which supposedly gives much better scans / color.  
> in terms of the difference, i do feel that 5.5 with negafix gives 
> better results than without it--however, i only used 5.0 for only a 
> day or so. i upgraded because it only cost me $10.00 to do so (a 
> special promo for polaroid
> customers).   however, i do believe that the 5.5 upgrade is only $45.00
> for those with other versions of silverfast--so it may be worth a try.

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