Hi Ernst and Mark. Thanks for you comments. Ernst, I have finally read your explanation on your website and understand (I think) the plots you show. The "bright" papers fluoresce in blue area making that part brighter. How big a difference in the vertical reflectance axis can one see in reality with the naked eye?
The total scale of 0 to 100% reflection is visible, from a black glossy vinyl with L 2.5, along newspaper and the oriental papers to papers that get above L 95 reflectance. All of them are in respective maps and can be compared to one another by eye (me) and in the plots. In practice it depends on the light that shines on the paper of course, more UV light will give a brighter reflectance with an OBA paper. In light with low UV there are OBA free papers that have a higher white reflectance than some OBA papers.
For the same conditions throughout (D50) check the Lab numbers also visible if you put the cursor on the name of the paper in SpectrumViz and see what the L an b values are of papers you know from your own experience. The higher the L the more reflectance, the lower the b : -2 to -10 the more blue/colder the paper is, in 99% of cases indicating OBA content. That will also tell you something about a paper that is in my list but you do not know yet.
The spectral plots are more technical and tell me whether papers are identical or where they differ, where in/on the paper OBA is applied, a bit about other whitening agents in the coating etc and how opaque a paper is.
Met vriendelijke groet, Ernsthttp://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2012, 500+ inkjet media white spectral plots.