From: Sandy King (sanking@clemson.edu)
Date: 10/27/01-08:19:51 PM Z
Judy Seigel wrote:
>
>Anyway, Sandy, I, too, tested the BLB against the BL, and found the BLB 20
>to 25 % slower... in cyanotype. My neighbor began with the BLB and
>complained that they were slow. I brought him over my BLs for comparison.
>He thereupon switched to BL. Then I brought his BLBs over here and tested
>them again (also in cyano), and found similar results -- 20 to 25% fewer
>steps in a given exposure time.
>
>The tests were made with Stouffer 21-step & I have them on file.
>
You need to clarify something for me. Above, you wrote that a
neighbor brought his BLBs over here "and tested them, and found
similar results -- 20 to 25% fewer steps in a given exposure time."
From the above I assume you infer that the BLBs in question were
slower than the BLs.
I assume this is some kind of error of expression, if not of
understanding, on your part, since the basic point of my discussion
was the *speed* of these processes with different light sources. The
fact that your neighbor found 20 to 25% fewer *steps* in a given
exposure time in his tests with BLBs says absolutely nothing about
the *speed* of the process. By convention, for both negative and
print emulsions, speed is determined by the first maximum black
recorded ( or some % of maximum black). The number of steps recorded
determines exposure scale (ES), or contrast, but has nothing at all
to do with speed. In fact, what your neighbor apparently observed was
that the BL tubes produced images of less contrast than BLBs.
You may want to have another look at the archived Stouffer step
wedges and restate your opinions re: speed.
Sandy King
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