12x16" enlarger - which lens ?

[plaubel]

You have to post pictures !!

Sorry, the parts are well stored; no chance to bring more pictures the next weeks - or months.
Do you know a garage totally full with things, and the important thing is behind left, on the floor ?
After a move I first filled the room, and now I have to clear the room, step by step;
after this, I may start to build the new dark room off this room...

""Looks
like you have the firepower to handle a very thick diffuser""

Drew, the Holux hasn't any diffuser; each 4 of my 8 Xenon bulbs are crossed ( horizontal/vertical in principle ); for me it looks that the 8 bulbs give even - and more than bright - light.
But I'm not lucky with this bulbs; they are expensive, they are very dangerous, and they are hungry for voltage.
Maybe I will try them, but I'm not sure.

Maybe the 305mm isn't the best solution, so I can go with a longer lens, too.
355mm also will be fine, and using some math will clear the possibilities of longer lenses in horizontal projection...
A lot of maybees at this point...

Heat isn't a problem, I grabbed the original fan.
But your idea that the transportation of the heat may not function with vertical position is a very good point.
Haven't thought about this !

Bob, the baseboard is heavy like plumbum :-)
I can't imagine how to install it moveable without a ton of more steel.
Maybe I will construct a non moveable board, we will see.

[Drew Wiley]

Evenness due to bulb configuration doesn't solve your hypothetical problem. As you go wider in lens angle, you get more illumination falloff, just like in taking lenses. But it's also relative to the working aperture. So once everything is set up, you make a relatively high-contrast (hard grade) test print, just to see how
well the system work, before you customize a diffuser. No diffuser and you nuke your negs with UV. These things were originally made for special graphics work, not general photo enlarging. And it is hard to know how well the bulbs survived the move. They should have been removed first. Then the weight. Hope you're on a firm slab. For ventilation, I'd recommend an exterior-mounted pull fan. Pulling air is a far more efficient method than pushing it; and you've get the fan noise isolated that way too. Oh boy, this sounds like fun stuff! You'll have some dicey moments getting everything ironed out; but what a machine!

[bob carnie]

Drew this looks like a photo enlarger not graphic arts.. do you know what applications it would have been used for other than photo.

It has a vacuum easel and I have never heard of this unit. it puts my 11 x14 Devere 515 to shame.

[Drew Wiley]

It's quite similar to the big Italian Pawo's. They were used with screens, generally for projection separations needing very high luminance rich in UV. There would
be no conventional photographic application for these. Big muscle large format heads would have been designed horizontal instead to begin with, for mural work.
You could take one of these to print directly onto Azo or maybe even platinum, provided you find a relatively rare lens optimized for UV transmission, along with
analogous enlarger glass. All the gasketing with have to be high-temp aero silicone. That has actually been done a few times; but that concept is self-defeating due to the significant skin cancer and eyesight hazards of open UV. I wonder if anyone here has seen the granddaddy of all UV enlargers - the carbon arc Fresson
unit, for that direct-carbon process?

[bob carnie]

Ok - I missed the part about UV light source... I wonder if someone with a good head on their shoulders could retrofit the exposing head with suitable lights for regular enlarging.

[Drew Wiley]

Sure, the heads can always be reconfigured. Durst built these kind of rigs too, but only up to 8x10, yet similarly vertical for modest enlargement. I don't recall the exact type of plates that were exposed with these, versus regular stat cameras, which used film obviously. But the specialty outfit I dealt with way back when I had a hot (literally) color mural enlarger still sold the xenon tubes; so these were still apparently in limited technical usage around here, maybe early circuit panel
prototyping with resists. I remember one of these enlargers rotting for sale forever in a basement, because the dealer wouldn't compromise a cent of the price of the dinosaur. I've seen several 11x14's up for sale in recent years.

[Bob Salomon]

Sure, the heads can always be reconfigured. Durst built these kind of rigs too, but only up to 8x10, yet similarly vertical for modest enlargement. I don't recall the exact type of plates that were exposed with these, versus regular stat cameras, which used film obviously. But the specialty outfit I dealt with way back when I had a hot (literally) color mural enlarger still sold the xenon tubes; so these were still apparently in limited technical usage around here, maybe early circuit panel
prototyping with resists. I remember one of these enlargers rotting for sale forever in a basement, because the dealer wouldn't compromise a cent of the price of the dinosaur. I've seen several 11x14's up for sale in recent years.

Afraid that is not quite true. Back when I was a RecTec technician in the USAF in the early 60s we regularly printed 9x9" aerial negs on both Durst and Homerich enlargers. And those were not custom military enlarger's. They were common, off the shelf units. Big shelves though.

[Drew Wiley]

Bob, you obviously know your stuff; but so do I. I have some components from the same outfit that did Durst's custom aerial neg enlargers, and have even seen
the guts for the custom colorheads. We're talking early 90's technology here, not 60's, actually the last of the true industrial Durst production, never for sale to the public. The NSA bought them and installed them in a facility where ZERO digital technology was allowed. They wanted a double-blind system that couldn't be fraudulently manipulated. The other advantage was the intuitive ability to assess real aerial film images, versus specialized analysts. In other words, rapid assessments can be made with big true-color enlargements, like a spotting scope, and then afterwards specific details can be homed in on via satellite or drone imaging. Astronomers have an analogous problem. They rely on smaller scopes used by amateurs to first discover a comet or asteroid, and then tell the big observatory pros where to look with the fancy gear. Of course, decisions are ultimately made by politicians and other big egos who might or might not respect
the facts, but that doesn't discount the technological advantages themselves. I have no idea if these units are still in use. If they are, nobody is supposed to know about them anyway. I do simply because of my own analogous design needs, asking around.

[Drew Wiley]

Oh, forgot. That basement unit I was talking about was specifically tricolor, sequential that is, for three separate color separations via high-output xenon onto a
pin-registered easel. Gotta be a different use than film, more like some kind of sensitized plate. Much gnarlier tubes than for photographic mural use. When I first
contemplated taming one of these, I was working on a water-cooled colorhead. But I already had a colorhead that would punch a 30x40 Ciba with a .90 supplementary mask in a matter of seconds. The damn thing shot my utility bill through the roof. So I went back and rethought the whole problem, and ended up
with something unique, with superb color, which actually runs cool - a much better design than Durst's, in fact, but also damn schizophrenic electronically. I'm
doing psychoanalysis on it again! That why I did recently install a parallel conventional Durst 8x10 color unit, as a backup.

[Bob Salomon]

Bob, you obviously know your stuff; but so do I. I have some components from the same outfit that did Durst's custom aerial neg enlargers, and have even seen
the guts for the custom colorheads. We're talking early 90's technology here, not 60's, actually the last of the true industrial Durst production, never for sale to the public. The NSA bought them and installed them in a facility where ZERO digital technology was allowed. They wanted a double-blind system that couldn't be fraudulently manipulated. The other advantage was the intuitive ability to assess real aerial film images, versus specialized analysts. In other words, rapid assessments can be made with big true-color enlargements, like a spotting scope, and then afterwards specific details can be homed in on via satellite or drone imaging. Astronomers have an analogous problem. They rely on smaller scopes used by amateurs to first discover a comet or asteroid, and then tell the big observatory pros where to look with the fancy gear. Of course, decisions are ultimately made by politicians and other big egos who might or might not respect
the facts, but that doesn't discount the technological advantages themselves. I have no idea if these units are still in use. If they are, nobody is supposed to know about them anyway. I do simply because of my own analogous design needs, asking around.

Drew, I was printing Cuban Crises images as well as images from integration when we flew the Univ. of Alabama and the Univ. of Mississippi during the early 60s with those enlarger's. Not in the 90s.