On 05/26/2011 01:00 PM, Klaus Karcher wrote:
Hello Barry,
I set up a database with approx. 60000 spectral measurements (amongst others many drawdowns of hand-grinded oil pains prepared with ancient pigments after historic recipes in the context of a research project) and found that neither the ColorChecker 24 nor the ColorChecker SG can adequately represent the spectral properties and "metameric challenges" of typical cultural heritage objects to be scanned -- at least not with the sensors and light sources I was confronted with. I chross-checked and confirmed my finding by means of relevant sub-sets of the SOCS Database (ISO/TR 16066: Standard object colour spectra database for colour reproduction evaluation) as well as additional spectral data from paint manufacturers.
My research took more than two years and resulted in a tailor-made scanner calibration and profiling target exclusively for Cruse Scanners (with 809 patches). Tests with prototypes are successfully finished and we are starting to manufacture the target right now.
Klaus Karcher
Hello Klaus, Given successive changes in pigment qualities through time I wonder how it works if say you have several reds in that target that are based on different pigments ranging from the 12th century up to now. They have to be selected as an average of used pigments through time and by that are a compromise again. Would it not be better to make more targets with pigments that represent a certain period in time and/or type of art? Still a rough classification considering the different speeds in adapting new pigments per area. What was ground by Jan van Eyck in 1420 may not have been in use in Russia two centuries later. -- Met vriendelijke groeten, Ernst Dinkla Gallery Canvas Wrap Actions | Dinkla Grafische Techniek | | www.pigment-print.com | | ( unvollendet ) |