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RE: filmscanners: Vuescan: "device RGB"

>> Vuescan uses a hard-coded tristimulus transform derived
>> from empirical testing of each scanner supported,
>> though this is presumably not the case for scanners
>> which happen to be supported just 'cos they understand SCSI
>> commands for another model.
>> ...
>       I understand Ed being wary ... At one time I was under the impression
>he was characterizing the scanners Vuescan supported, but you seem to
>claim some scanners are not characterized.  For example, did he take
>the time to chacterize the LS-40, for which he added support in a
>single day??  If he offers a color space option which is "implied" to
>belong to the device, this is important to know.

The following may be found in the vuescan help file - Introduction:

  VueScan uses color correction tables which have been derived 
  from a Kodak Q60 calibration slide and which produce colors 
  accurate to better than 1%.  The default color primaries and 
  white point are the same as used by the Kodak PhotoCD system 
  - Rec. 709 primaries with a D65 white point.  

And from a post from Ed last January:

  Most scanners return raw data straight from the CCD.  Some
  scanners do color conversion internally.  The Epson scanners
  all (optionally) convert colors to sRGB before returning it to 
  the host computer (this is the mode that VueScan uses).  Other
  scanners (i.e. HP) let you download a 3x3 matrix to do the
  color transform in the scanner, but I never use this in VueScan.

To interact with Ed in a public forum -- from the Vuescan web page:

  If you'd like to exchange tips with other people
  using a wide range of different scanners, try
  the comp.periphs.scanners newsgroup.

Bob Shomler


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