From: Judy Seigel (jseigel@panix.com)
Date: 10/27/01-04:14:31 PM Z
On Sat, 27 Oct 2001 FotoDave@aol.com wrote:
> << 5. The *Big* surprise for me was that the GE BLB tubes were also much
> faster than the BL tubes (and of about the same contrast). In fact,
> the 20 watt BLB tubes were even faster (by about 1/2 stop) than the
> 75 watt Super Actinic tubes!!! >>
Look guys, if we're not going to insult Australian Aborigines by calling
them Abos, could we please cut that stuff about URBAN myths? As a firm
exponent of urban values, which I find no more susceptible to myth than,
say, farmland, could we please say something like "received fallacy"?
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.
Here are my speculations about your unexpected findings ... First of all,
you're using bulbs by two different manufacturers... that to me is more
suggestive than anything about temperature or humidity -- which I find not
particularly important within normal room conditions assuming exposure and
development are PROMPT). The thickne & composition of the glass and source
of the phosphors are almost certainly NOT the same.
Secondly, the manufacturer doesn't send us a printed announcement when
he/she changes specs.. the glass for either of the bulbs could have been
changed.
Thirdly, I was advised by Voltarc when I observed that my BL Bulbs emitted
different light -- even bought at the same time, some looks pink and some
pale blue -- that that's a factor of the particular phosphor they got from
the mine in that shipment.
Fourthly, you don't know how long your bulbs or mine either of either kind
sat on the shelf, in the store, also in your studio. Do we know that
phospors in vacuum or other conditions don't undergo changes?
Do we know that amount of phosphor applied is scientifically (let alone
cyantifically) standardized?
If you made your tests at different times, did you have a voltage
regulator? Did you use the SAME step tablet, with the paper in the same
part of the light bed?
Also, as Dave asks...
> Sandy, is the age of the tubes taken into consideration?
I don't know how many peppers (are they all fat or are some thin?) your
program will afford the following, but IMO this project is NOT as simple
as it might seem. There are hidden variables and booby traps (we now see)
at every turn. If my results and your results are so different.... how can
either of us speak for someone, for instance, in Brazil who may be
usaing oddball old lamps, or getting them from some oddball gray market,
or using a bellows & diesel engine for power, or maybe a cover glass which
screens rays differently, or.... about a dozen other variables I'll think
of one of these days...
So maybe it's possible that the most definitive conclusion of this project
may be telling us that these variables vary...
J.
This archive was generated by hypermail 2b30 : 11/02/01-08:55:27 AM Z CST