Interesting. I have tested new BL and BLB of the same manufacturer
side by side in the same ballast and never observed a difference of
anything at all of this magnitude with any process. In my tests the
BLs did print slightly faster, but the difference was more on the
order of about 1/4 of a stop, which is about what it should be based
on the SPD charts for these tubes. The BLB is the same tube as the
BL, the only difference is that it has a Woods filter that cuts out
all light above about 420 nm.
Just for the record, my exposure in cyanotype with BLB tubes, with
the tubes at four inches from the printing frame, is about six
minutes. This is for negatives with a shadow density of about log
0.20,
Sandy
>My BL tubes arrived today! They replaced the BLB tubes I have been using.
>I find an enormous improvement. Same paper, same sensitizer (classic 1:1),
>same fixture (except for the bulbs), same day. Old exposure 15 minutes. New
>exposure 3 minutes.
>Charles Portland OR
Received on Tue Nov 15 10:51:20 2005
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