John Rudiak (wizard@laplaza.org)
Mon, 28 Jun 1999 22:05:08 -0600
I can offer an observation, take it for what you think it is worth.
Last year I printed a portfolio of original 12X20 superXX negs souped in Pyro.
(Sounds like it should be heaven, huh?)
The exposure unit I was using for this job is made up of 12 four foot BL
blacklight tubes spaced less than 1/4 inch apart.
The negatives were developed by inspection (fog?) and the film stock (a large
lot bought all at once because of it's special cut) was out of date and a
little foggy from that.
Negatives I make (dupe or original) print between 3 and 6 minutes (unless I
mask) under this source.
This negative (one of 12 similarly produced that needed to be printed) took 35
minutes to expose. Since this wasn't the densest negative of the lot, I was
looking for some alternatives because a number of portfolios had to be made
from this set of negs.
David Kennedy and I had been talking about bulbs, etc. for a while and we
decided to print the same neg underr his unit, trying to make that the only
variable. David nakes some pretty gutsy negatives "cause it it what he needs to
get the look he is after, and I knew that his exposure times were shorter than
I though they should be. I brought paper of the same lot, my own chemistry
(same batches that I used to make the print under my box) my own brushes, you
get the idea.
Davids box has three foot super actinics rated at 90W each, spaced the same
distance apart as mine are, and uses the same bulb to paper distance as I
do...........
To get the same highlight density as my 35 minute exposure took 6 minutes.
The print was noticeably flatter, with the same chemical mixture.
Considerations:
His bulbs pack 90 Watts into three feet (30 Watt-Feet?) My four footers at 40
Watts have 1/3 the output per foot. ( This is to address the attitude that the
difference in wavelength is causing the exposure change. I maintain this may
be true to a degree, but feel it is overrated as to its effect).
These bulbs have a reflector inside them that directs the light downwards,
increasing the quantity of light reflected downward. More downward lumens per
Watt. So the bulbs are three times stronger per foot to start, and then more
of it gets to the print.
There are clearly reciprocity/contrast effects occurring, accented by the
self-masking. It is most probably not the wavelength difference causing the
contrast difference, but this is my feeling from observation and experience and
was not tested.
Conclusion- Yes, they're faster, but probably not for the reasons that have
been discussed here. A Shelby Cobra is faster than a Corvette (similar
vintage), but not because one's red and one blue, but because the Cobra is a
Corvette on steroids. It's hard to beat more horsepower in less space. (I know
there are a lot more differences- please car guys- don't jump on me- making an
analogy)
The solution to the original problem? Remake all the negative so they print
under six minutes in my darkroom.
John
http:ww.johnrudiak.com
"Jeffrey D. Mathias" wrote:
> William Laven wrote:
> > ... In my tests, Super Actinics, which emit a narrow
> > band peaking at 420nm, print faster then traditional "black light" bulbs,
> > which emit a broad band that peaks at 350 or 360nm. A friend of mine did
> > comparisons of BL vs. Super Actinics with POP and found the SA's produced
> > shorter exposure times and at least a grade's worth more contrast.
> >
> > Eric Neilsen did some comparisons of BL vs. SA for Pt/Pd, too....
>
> OK, I would like to see something written up on what comparisons were
> made and what the resulting prints showed.
>
> I was just printing, unfortunately at 88F since I haven't put an air
> cooler into my darkroom yet (still cooler than outside)(Didn't think I'd
> really need it up north here, but this dang el-ninya thing has given us
> a hot drought in Boston. I can control just about everything else.) I
> could not get enough exposure on AFO 66%RH. I tripled my exposure and
> the print showed about the same weakness. Then I went outside in direct
> sun, and wouldn't you know, a great print.
>
> Now I have always suspected that things may get exaggerated at higher
> temperatures. I am really wondering now just what influence the
> spectrum of light has on this process. It does seem to have a
> substantial contribution. So, if you all got some data, I would
> appreciate the details. If not, does someone have the ability to run
> some careful comparisons with various incident spectrums. Right now it
> makes me want to move back to the desert.
>
> --
> Jeffrey D. Mathias
> http://home.att.net/~jeffrey.d.mathias/
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