I understand your need of doing this but I don't understand why the result
seems always far from desired. The 4000ED and many other scanners are
calibrated to a certain degree of accuracy for slide. I seldom seen big
shift in Ektachrome and Fujichrome but Kodachrome seems another story. For
most of my scans a curve for contrast adjustment is already pretty good. If
slide scanning is so complicated I recommend you try a DSLR like E-1 or E3.
C.H.Ling
----- Original Message -----
From: "Fernando Gonzalez Gentile"
Yes, they clip awfully specially in the red channel, green and blue a
little less so; but they shouldn't.
Nonetheless, I was carefully matching what I was seeing in the
transilluminated Ektachrome to what I was seeing in a supposedly 6500ºK CRT.
From the consistent red - magenta shift ( and clipping ) I can only
blame the lamp: it may have frequency peaks in the green spectrum, so
when dominant color is blue, it shows magenta into the blue; and when
dominant color is yellow, it shows red into the yellow.
I think that what may be *ideally* needed is a light source which has an
even spectrum, that would properly be a pure white light source.
I certainly thought about what you had already advised me about using
the monitor as the light source, but the same rules: you're seeing
white, but in fact is a tristimulus (*) of red, green and blue. I ended
in not using it because, at least in my monitor, luminance is too weak
and colors shift away too bad. Worse than with my Philips lamp.
I cannot blame the Nikon on this one: if it has something wrong it could
be a blue cast, which I am about to investigate
In short: having an uneven and too intense light source what I find to
be the reason of my clipped scans with red-magenta hue. Naturally, this
reason rules after I had learned and practiced a little bit with the
scanner and photoshop, that is not a long time.
Did I make myself clear?
Thanks for answering (once more ... ), C.H.
Fernando.
(*) <http://en.wikipedia.org/wiki/CIE_1931>,
<http://en.wikipedia.org/wiki/CIE_1931#The_CIE_standard_observer>
"In the CIE XYZ color space, the tristimulus values are not the /S/,
/M/, and /L/ responses of the human eye, but rather a set of tristimulus
values called /X/, /Y/, and /Z/, which are roughly red
<http://en.wikipedia.org/wiki/Red>, green
<http://en.wikipedia.org/wiki/Green> and blue
<http://en.wikipedia.org/wiki/Blue>, respectively. (Note that the X,Y,Z
values are not physically observed red, green, blue colors. Rather, they
may be thought of as 'derived' parameters from the red, green, blue
colors.) Two light sources, made up of different mixtures of various
wavelengths, may appear to be the same color; this effect is called
metamerism <http://en.wikipedia.org/wiki/Metamerism_%28color%29>. Two
light sources have the same apparent color to an observer when they have
the same tristimulus values, no matter what spectral distributions of
light were used to produce them."
C.H.Ling wrote:
> Your images are poorly clipped, I never have a 4000ED scan like that.
> Don't
> understand how the scanning workflow related to your projecting lamp. For
> color adjustment of a scanned image I open a white box in PS and put the
> slide over it for comparison.
>
--
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