Digital BW, The Print

I've posted a graph of the paper white Lab B values for 2 brightened RC papers tested by Aardenburg Imaging.  The Lab B values in a brightened paper will increase as the OBAs fade, mostly due to oxidation.  This fading of OBAs will appear to make the papers "yellow" relative to their initial tones.  I wanted to see how a premium paper might compare to a paper that is less expensive.  I chose Epson Premium Luster and Red River UltraPro Gloss for the comparison.  See the graph at http://www.paulroark.com/BW-Info/OBA-compare-Eps-RR.jpg 

I've discussed the results with Mark at Aardenburg Imaging, and he thinks the initial dip in Lab B values for the Epson paper is probably within what might be caused by normal read variances.  I was speculating that maybe Epson had employed some sort of counter-fade strategy (intentional fast fading yellow to offset the initial OBA fade).

Mark thinks the major factor that distinguishes the results is that OBAs are often put in 2 locations.  The ones under the barrier of the RC papers are better protected from oxidation, which causes the fade.  OBAs are also often put in the coating above the RC barrier, where they are much more exposed to oxygen and fading.

Assuming that explains the initial differences, it's interesting that the premium and less expensive papers exhibited almost identical OBA fade after the initial 20 MLux Hours of exposure.  It certainly seems that the OBAs under the RC barrier are essentially the same.

Paul
www.PaulRoark.com