The 250 watt Halogen, 82 volt GE EVW bulb I had in the Beseler 45S head made its final blink and I replaced it with a UV producing Osram Halogen Photo Optic lamp with the same specification as the GE (same price too - $25). I've read that TMax-100 has a UV blocking filter. The question is whether or not blocking the UV produced by the bub affect printing the negative? I uually print with muti-graded paper but wanted to try printing on graded paper as well.
Thomas
Colorheads have built-in UV blocking filters. Just depends how much still gets through, and even into the film itself. Why not use TMY400 instead? But switching out your EVW bulb to something high-UV might prematurely damage your whole enlarger. It's bad for filters, gaskets, bellows, diffusers etc. Enlargers for UV need special materials. Even most enlarging lenses block some UV. You need the right type lens too. But don't forget the eye safety issues involved !!!
You can find EVW lamps for 6 to 8 bucks online no problem. If you want a GE there's NOS, Osram makes good bulbs. If you really have a bulb that's pumping out a lot of UV, which I doubt, I would get it out.Originally Posted by tgtaylor
In theory UV presence produces a change in the contrast grade as it works like blue, many papers are highly UV sensitive. As TMX base blocks UV you should notice less that effect.
Also UV reaching paper has an effect on sharpness, the enlarger lens may have UV transmission while it may not be corrected for UV, so the if paper is highly UV sensitive we'll see some soft focus effect, this is well described in Post Exposure book, Ctein. http://ctein.com/PostExposure2ndIllustrated.pdf , page 149
(http://photographyoftheinvisibleworl...t.com/2011/01/)
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PD: An interesting question is if Ilford contrast filters are blocking UV...
Last edited by Pere Casals; 7-Jul-2019 at 09:52. Reason: PD
Cheap bulbs usually don't last long enough to justify the seeming discount. Avoid Chinese mfg. GE no longer makes bulbs, but there are probably still a lot around. Be certain they're US made, since GE also imported junk versions. EU or Japanese Ushio bulbs are also good.
Are you sure the UV filtration is not removed in the fixer?
100% positive. Anyone who has tried making alt process prints from tmx negatives can assert that the UV filtration is inherent to the film itself.
Yes... in carbon and Pt/Pd UV printing exposure has to be 8 times longer because TMX blocks UV by 3 stops aprox. It has been said that the UV absorbing dye is in the film base plastic. Many plastics are manufactured with an UV absorber mixed in, in that way plastics are not damaged by direct sun rays over time. If the UV absorber is inside the plastic then obviously it would be extremly difficult to remove it.
While it is possible to use TMX negatives for alt UV printing it happens that exposure has to be very long, 8 times longer than usual, IIRC it was Sandy that measured this with an UV densitometer.
The question is why? TMX was originally engineered to replace a suite of older films, including some marketed mainly for technical applications, astronomical usages included. It was also recommended as a partial replacement for Tech Pan, which had extended red sensitivity, so UV cutoff would have been appropriate in similar applications. I have reason to believe that even now the bulk of TMX sheet film does not go to regular photographers like us, but to technical and industrial usage. So I have some hunches, but no definitive answer. Adding a UV blocker to protect the base from sunlight degradation wouldn't make sense. Who's going to stand out in the sun staring at the same negative for ten years straight? That PET base is pretty robust by itself; so this must have something to do with precise spectral sensitivity relative to intended ranges of use. My spectrograms of TMX100 vs TMY400 are out in the lab, so I can't check them at the moment, nor is the full answer likely to be found on ordinary photo forums. You'd have to check for scientific and forensic applications.
If Ctein's theory is right, (Post Exposure, page 145, http://ctein.com/PostExposure2ndIllustrated.pdf) then in certain conditions UV presence may led to a loss of sharpness in the print, if the enlarger lens is not well corrected for UV.
Perhaps Kodak wanted to address this potential problem... I cannot see another motivation (still it can be there...), because if the blocking is in the base then UV reaches the emulsion anyway during the taking, so mostly UV blocking would be intended for the printing. Of course I'm speculating because I don't know any source explaining why kodak does that.
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