Datacolor User to User Support Group.

Thanks CD, I'll delve into it knowing that the process is feasible.  I 
shoot the originals using studio mono lights with polarizing film etc. 
and a custom camera profile.  Despite all that the files still need 
tweaking, I guess that's the real world as well.

Ken

CDTobie@... wrote:
>
>
> In a message dated 4/25/08 2:53:50 PM, kenchow@... writes:
>
>
> Is it possible to use the spectrocolorimeter to directly measure color
> values from an original art work (watercolor, oil, acrylic) and relate
> them to a digital capture of that piece for the purposes of color 
> matching?
>
> Yes, though accuracy of this type of device (called a 0/45 device as 
> it views at zero degrees, and illuminates at 45 degrees) is highest 
> for flat surfaces, and less exacting for textured surfaces, or heavy 
> clearcoats over the colors.
>
> For example can RGB values from the original be measured or derived -
> then I can compare that to the RGB values of that section of the digital
> capture and determine how far off it is...
>
> Lab values are real world values, and contain factors not included in 
> RGB values. But a file with a reasonable "RGB to Lab relationship" 
> (meaning a file in a Photoshop RGB workingspace such as AdobeRGB) 
> would be capable of reasonably matching colors, within the colorspace. 
> Its a tricky business, since the "image" on screen also includes the 
> illuminant it was photographed under, and values in textured images 
> contain sheen and shadow factors.
>
> The easiest method would be to use the Lab values from the spot 
> measurements, and set the Photoshop info tool to read in both your RGB 
> space, and in Lab.
>
> I see from the documentation that Lab values can be measured, does that
> accomplish the same thing in some way?
>
> Whether you can achieve what you are attempting depends on a number of 
> complicating factors, but its certainly worth attempting. Using high 
> quality 5000k lighting when shooting the painting would be helpful, 
> and avoiding huge workingspaces such as ProPhotoRGB would assist as well.
>
>