[filmscanners] RE: Vuescan Color Tab

["LAURIE SOLOMON" <laurie@advancenet.net>]

Apart from the fact that I completely forgot that the discussion is
restricted in part to the domain of Vuescan's operation and not that of the
more general domain of all applications, I think that the difficulty
revolves around the distinction between the notions of a "raw scan," which
produces complete and unaltered data to the fullest extent possible of the
devices physical capability, and the notion of "device space," which
represents the optimum color space and gamut that can be reproduced by that
device sp as to represent as close as possible the raw scan data.  The later
using a color profile does interpret and convert the raw scan data,
rendering it into a specific color space in which the original raw data is
altered and lost in the translation so as to match as best as possible the
device's color space.

>From my understanding, doing a direct translation from the raw scan data to
any color working space, including Adobe RBG 1998, sRGB, ColorMatch, or
device specific color profile, would have the same effect.  Thus selecting a
more general or better working color space with the widest gamut would be
the best choice in that it would capture a more accurate and complete
rendering of the raw scan data than a specific device profiled color space
would and would provide for greater future flexibility without any
additional quantization errors and extra dithering. This would especially be
the case if the resulting product was to be an archived copy.  However, the
best alternative, in my opinion, for archive copies is to archive the raw
scan data as is just as you do and not transform it into any particular
color space until the time of use when one knows the requirements of the
output devices which will be used for outputing that specific use.

In the case of "device RGB" with respect to Vuescan ( or any other
application for that matter), it is questionable what device is being
referred to and what color space and/or gamut is being used.  In such a use,
the term "device" appears to take on such a generic meaning that "device
RBG" could mean sRGB or it could mean any applicable device profile that
one's color management engine uses to display the output ( i.e., a specific
or generic monitor profile).

At any rate, I think that we are really on the same page and that it is only
a miscommunication which was probably caused by either a misreading on my
part or a confusing response on my part.  I come to this conclusion after
re-reading the previous posts more closely.  As always, it is always a
pleasure engaing you in discussion whether we agree or disagree. :-)



-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of michael shaffer
Sent: Tuesday, May 20, 2003 4:57 AM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Vuescan Color Tab


Laurie writes ...

> >   I say it's "alright" because there's nothing wrong with it.
> > However, if you did decide to convert from "device space" to another
> > space before archiving, and then wanted to convert again later to a
> > "better space" (for whatever reason), then you need accept the
> > additional quantization errors and extra dithering ... i.e., two
> > conversions rather than one.
>
> This may be a language problem; but by device space, I assumed that you
> meant the native color space profile of the device (scanner or camera).
> This native space is often smaller than most traditional working spaces
> (e.g., Adobe RGB 1998 or Color Match) resulting in a loss of raw data
> unless - ...

  There should be no loss of data ... unless Vs does something unjustified
(by anyone's understanding of "device space") if "device RGB" is selected
... I don't use it, and archive the raw scan.  In any case, the way device
space should work is, ... no data is lost because the RGB data is not
converted ... it is still the device RGB, as scanned, and the device space
is assigned.

  It seems to me you may be correct about Vs's definition of "device RGB",
especially for scans of negatives.

cheerios ... shAf  :o)
Avalon Peninsula, Newfoundland
www.micro-investigations.com (in progress)


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