From: Eric Neilsen (e.neilsen@worldnet.att.net)
Date: 06/24/01-10:28:05 PM Z
I beg to differ Judy, but the BL and BLB give out different amounts of
light. The bell curves on these by several manufactures will attest to
this. They both peak at or very near 360nm but the BL puts out more light,
about 20% more as GE measures it using the BL as their bench mark.
----- Original Message -----
From: "Judy Seigel" <jseigel@panix.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, June 19, 2001 12:01 PM
Subject: Re: correction re: lights
>
> > There are BL and BLB. BL stands for BLACK LIGHT and the BLB for BLACK
LIGHT
> > BLUE. BLB lamps have a blue-violet coating inside and therefore block a
lot
> > of the visible spectrum.
>
> Exactly.
>
> But this thread is the perfect illustration of good and bad from "the
> net," warping, misconstruing, needlessly complicating and generally
> bollixing up what is actually quite simple.
>
> I have tested most "alt" media under several lights, although not each
> under EVERY light. Still the similarities are greater than the
> differences, and the thing now looks to be getting out of hand....
>
> The so-called "aquarium" lights are the AQA bulbs, and are liked for pt/pd
> because the output supposedly peaks at 414 nm, pt-pd's greatest
> sensitivity. But there are always other spikes down the line and different
> mixes have different precise sensitivities anyway, so the practical
> difference between those bulbs and regular BLs is dubious. I myself found
> NO difference in use in other media.
>
> Again, although processes such as gum nominally peak at 360 nm (which is
> claimed highest output of the BL bulbs), depending on the color of the
> pigment and the mix there are other spikes as well. The distinction if any
> in use is trivial.
>
> Similarly for the "metal halide" bulbs. Or at least the metal halide bulb
> I tested with for 10 years. There were differences between it and the
> fluorescents, but they were not as great as differences caused by emulsion
> mixes and they were not consistent along the line. There's also the fact
> that your cover glass is a factor in the equation, so any "rule" may well
> work only with that glass. And the other fact that one adjusts one's
> emulsion and exposure to fit the light source, which further irons out
> differences, if any.
>
> The BLB bulb incidentally, gives EXACTLY the same output as the BL, but
> the (expensive) glass it's sheathed in permits only a narrow wavelength to
> pass, so things get that glow in the disco. It will print whatever, but
> with less light is simply slower about it, and lacking some other spikes
> is probably a different "curve" --- maybe. But again, other factors and
> ingredients affect that curve, too.
>
> There is however strong testimony that the superactinic fluorescents (see
> P-F Sources & Services) give not only greater speed but "nicer" contrast
> for pt/pd, or so several users have testified.
>
> PS. As noted there are a couple of new -- and old -- setups in P-F #6.
> But there's no reason anyone should spend more than say, $150 and half a
> day to build a light table... Unless you're trying to avoid photography.
>
> Judy
>
> .................................................................
> | Judy Seigel, Editor >
> | World Journal of Post-Factory Photography > "HOW-TO and WHY"
> | info@post-factory.org >
> | <http://rmp.opusis.com/postfactory/postfactory.html>
> .................................................................
>
>
>
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