this Web page last updated July 21 2005.
I've looked at 10 8-inch pieces, using polarizer and LCD screen. I had some afternoon backlighting in the testing room, which created some artifacts on the photos. But of the 10 disks, only two stood out.
Plate #2 has a notible flaw, a bubble or internal ding.
#2 glass on screen no filter
#2 glass viewed through filter
detail of flaw #2
closeup of flaw
Plate #10 has bands of variation that are more pronounced than other plates.
#10 glass on screen no filter
#10 filtered section, enhanced - structure not visible otherwise
filter on glass, closeup #3
filter on glass, adjacent location, Closeup #4
The other plates may have some variation but it's hard to see it. Testing in a dark room may be necessary to reduce reflected artifacts. To see some variations requires digital photos and ehnancement, as the ringed structure on #10.
Herb JohnsonContact information:
Copyright © 2005 Herb Johnson