Digital BW, The Print

Tony Sleep wrote:

" I missed the original, but the idea that OBA's cause metamerism is not
right. If you use carbon inks on OBA paper, you do not suddenly get
metamerism. Bromides containing OBA's did not display metamerism.

Metamerism is due to some ink pigments themselves reacting to UV with a
degree of flourescence, causing a shift in the intensity and/or frequency
of reflected light, and the image colours to change in an unbalanced
manner."

Tony, thanks for your comments on my post and your valuable additions.
However, metamerism is defined as a shift in colors under varying lighting
conditions and significant fluorescence under UV will indeed cause a shift.
It may be a lot more subtle than the metamerism exhibited by carbon pigment
inks, but it's still there. There's simply no way an image on neutral white
looks like the same image with a fluorescing background. Subtle yes. Non
existing, no. Last, I completely agree with your statement about OBs
potential for fading which reveals the underlying yellow of the paper. This
all came up in the context of my consulting to Crane given that Museo papers
have no OBs yet they are also quite "bright."

Rick Colson