I'm trying to find a good database of absorption or reflection spectra in visible light for pigments. I've found a wonderful database in this article: http://e-conservation.org/issue-2/36-FORS-spectral-database#CSV It's almost exactly what I needed Except I don't understand the data The graphs in the article show a lot of reflectance values over 100% (and doesn't explain them) and the data in the CSV files have both numbers greater than 100 and lower than 0 (negative numbers), not to mention I don't know if those values are percentages (the same on the graphs of the article) or some signal intensity value. I can't seem to find explanation for these things on the article. Can anyone help me? Thanks!