a UV enlarger?

[wildbillbugman]

Think of the Danger ! It would be dificult to minimize the chance of accidental exposuing of ones retinas to intense U.V.
Bill
What of Pastic Lenses. Many platics need u.v. blockere added so as to NOT transmit U.V. I know that plastic lenses are used only in cheap toy microscope, telescoipes asnd such. But maybe there could be a real, valid use for plastic lenses.
Bill

 

[JBrunner]

If you made something with such an intense UV light source, it would probably be pretty bad for your eyes =O

No worse than the the NuArc xenon lamp I and many others use for contact printing alt process. It simply takes common sense. It's not like you hang around for the exposure, staring up into the light source(it takes anywhere from 5 minutes to half an hour, depending on the negative and process). You close the drapes, turn it on and leave it to expose. A UV enlarger would be no different at all, and as a matter of fact, probably would emit less stray UV than a glass topped contact printing frame, or plate burner such as I use. It's a completely viable idea, and in my opinion, once constructed, would be much faster and easier than the difficult, expensive, and time consuming negative-positive-negative shenanigans involved in enlarging a negative (been there, done that, got the T-shirt) .

 

[holmburgers]

The fear of burning your retina with a grain focuser is probably valid. But you could focus with blue light to get you in the ballpark and at the very worst, what, a small focus shift?

I bet a physicist could tell us, but would UV focus shift as badly as IR? It seems that there might be less refraction with the higher frequency of UV light. I dont know though... just speculating.

 

[JBrunner]

The fear of burning your retina with a grain focuser is probably valid. But you could focus with blue light to get you in the ballpark and at the very worst, what, a small focus shift?

I bet a physicist could tell us, but would UV focus shift as badly as IR? It seems that there might be less refraction with the higher frequency of UV light. I dont know though... just speculating.

You don't need to focus mirrors.

 

[keithwms]

UV focus isn't hard at all with APO enlarging lenses. I've done UV photography with them, no problem. Regarding the focus shift, it is indeed an effect similar to what you get for IR. But it's an easier problem to solve: you can measure the distances very precisely and do some tests, unlike the usual situation with IR photography.

Jason, I think you mean that you don't need to correct focus with mirrors. You do still need to focus mirror lenses

Regarding eye damage, if you're looking at light reflected off your focusing paper then eye damage isn't much of an issue. With deep UV light you get some fluorescence from the paper and it's not nearly as damaging to the eye as direct UV. If worried: you can just wear UVB-proof glasses and no worries. I have focused deep UV quite a lot.

The main health concerns with high power UV light sources like deuterium lamps are: (1) ozone production in a closed space, and (2) skin cancer risk from exposure.

Regarding enlarged negs, what I have done, and what works very well in my opinion, is to shoot with a tolerant slide film like Astia, then enlarge that to a panchromatic b&w film such as tmax. That way you don't have to make an interpositive or whatever. But dr5 works very well, of course, as long as you pay attention to the comments on their site regarding which films work best with the process and what speeds to use.

Regarding my previous comments, I certainly don't mean to dissuade anyone from experimenting. On the contrary! Just be aware that many people have thought about this for a long time and there are reasons why you can't just buy some UV enlarger from freestyle

 

[holmburgers]

Right on.

I've been doing a little bit of history reading and I believe it was John Draper who first realized the need for a focus shift with daguerreotypes to secure the sharpest results. However, this is with very simple, uncorrected lenses. Alexander Wolcott's camera had a such an improvement in speed (due in no small part to this UV phenomenon I'm sure!) that he revolutionized portraiture with the dag. However, "quicks" and accelerating solutions soon obviated his system.

It's good to know that mirrors would require no focus shift and indeed that makes sense.

 

[steven_e007]

Has anyone made a Wolcott mirror camera recently? (say, in the last century? )

I have never seen one working. The thing that bothers me is that the thing is so 'open'. The plate is protected from the light only by facing away from it. I assume this worked only because the emulsion was so very slow in those days. I would have thought a modern film, even a slow one, would fog very quickly from stray light (you could surely never get the inside black enough not to get some light scattered back onto the film?) Modern mirror lenses of course use additional optics to put the film behind the shutter in a light proof box - but then the anti - uv properties of the glass are back...

Getting back to enlargers - has there ever been a Wolcott enlarger? How would you get around the optical path problem of the negative and light source being 'in the way' of the mirror?

 

[holmburgers]

I think the negative "being in the way of the light source" is not a problem at the plane of focus. It's just like a catadioptric mirror lens; the out of focus areas will show evidence of that void in the form of circular bokeh. But, on the plane of focus a full image is formed and since a negative is flat, a respectable image should result.

Somebody correct me if I'm wrong, but I think that's the gist of it.

 

[DREW WILEY]

UV enlargers have been commercially made, and it wouldn't be hard to design one. Special lens and
neg carrier glass, of course. I'd want a water-cooled coil jacket around the head. All the internal
gaskets and bellows material should be pure silicone rubber. Anything near the light source itself,
hi-temp aircraft silicone and heat-resistant truck wiring. Stainless steel mirror box to tranfer heat quickly into the water jacket. Common-sense eye protection (you wouldn't even need to be around the exposure unless you needed to dodge and burn; but that could be done on masking sheets in advance.) Trying not to cook your negatives would be another issue, but with the right lightpath, the length of exposure shouldn't be much longer than typical. You'd want it rigged to 220V of course, with one helluvacircuit breaker. I made something similar once and my utility bill doubled!

 

[Mainecoonmaniac]

I prefer the free, nuclear fusion orb. AKA the sun. Way easier for simpletons like me to use. Maybe I can Jerry-rig a tanning bed into a UV printing box?

 

[keithwms]

I prefer the free, nuclear fusion orb. AKA the sun. Way easier for simpletons like me to use. Maybe I can Jerry-rig a tanning bed into a UV printing box?

Sure but just bear in mind that what's best suited for the skin is probably not best suited for your emulsion The sunbed plastics probably block some bands you'd like to expose with. But your basic, clear PMMA acrylics (perspex / plexiglas) are transparent way down past common glass.

 

[steven_e007]

I think the negative "being in the way of the light source" is not a problem at the plane of focus. It's just like a catadioptric mirror lens; the out of focus areas will show evidence of that void in the form of circular bokeh. But, on the plane of focus a full image is formed and since a negative is flat, a respectable image should result.

Somebody correct me if I'm wrong, but I think that's the gist of it.

Yes, I'm sure you are right, maybe some funny rectangular structures in the out of focus areas is the only drawback in a Wolcott camera.

I was thinking more that using the same configuration for a 'Wolcott enlarger' would mean the mirror bounces the image straight back at the enlarger head - whatever the light box is.

How would you fire light through the negative and then focus it onto the paper without the negative carrier and light box getting in the way?

Sounds like extra mirrors and some lateral thinking is required to come up with a workable configuration.

 

[holmburgers]

steve, I had the exact same thought last night!

I think the simplest way to do it would be that the UV source would have to be nestled in that little area behind the negative, or in the case of Wolcott's camera, behind the sensitive plate. The image would then project out of the camera.

Could you fit enough LED's behind the negative? IDK...

Drew, what did your enlarger look like, or was it normal with just a heckuva light source?

 

[steven_e007]

Enough theorising already!

The packs of LEDs are on their way.

Well.... someone had to have a go

 

[Mainecoonmaniac]

You're braver than I am!

Enough theorising already!

The packs of LEDs are on their way.

Well.... someone had to have a go

Remember, protect you retina! Tell us APUGers what you find out!

 

[steven_e007]

Frustration, frustration, frustration!!!!

Things are manic at work, my boss is keeping my nose to the grindstone - I was working away from home this week so didn't even have time in the evenings....

And at the weekends? Well, the wife is WORSE. Fliiping DIY - "In time for Christmas". Last weekend was plastering the wall, fitting architrave and papering (yep, just about took all weekend...). This weekend it will be the rest of the architrave, painting and fitting the carpet strip.
Then next weekend?
Christmas shopping... I just know it.

How is a guy supposed to do any photography around here? :confused:
Let alone experiment with enlargers and LEDs...

Bah humbug grumble grumble... [/rant mode]

So, the LEDs and resistors have arrived - but haven't found time to do anything with them, yet.

Watch this space (er, but no need to rush...)

 

[holmburgers]

Excited to witness the saga!

 

[JBrunner]

Sure but just bear in mind that what's best suited for the skin is probably not best suited for your emulsion The sunbed plastics probably block some bands you'd like to expose with. But your basic, clear PMMA acrylics (perspex / plexiglas) are transparent way down past common glass.

Built a UV box with like 15 UV "blacklight" tubes from home Depot. Wayyyyy slow. Then I got the Nu Arc. Life got better.


Steve, forgive my Yankee ignorance, what is "architrave"?

 

[steven_e007]

Built a UV box with like 15 UV "blacklight" tubes from home Depot. Wayyyyy slow. Then I got the Nu Arc. Life got better.


Steve, forgive my Yankee ignorance, what is "architrave"?

Not sure myself, and I've probably spelled it wrong, but it is the extra bit of carved wood trim that fits around the door on top of the door frame.

So... the DIY is finally finished. Yeh!

But it's Monday morning... back to work. Oh hum.

 

[keithwms]

I have one of those really old UV contact printers, it weighs a ton and has some 20 argon bulbs, each individually switchable so you can dodge and burn Quite a gem. Alas the argon bulbs seemed to have lost much of their juice.

If I wanted to make a UV enlarger I guess I would us a ULF camera with paper in the film holder, and just put the neg on a UV source like my argon bank. Maybe I'll try that with my 11x14.

Actually, UV lasers are now readily available, so if you had a rastering stage under the neg, you could in principle make a very large enlargement quite quickly. I don't know how much quickly you'd want to go though before you start cooking the neg.

 

[steven_e007]

I've thinking about the scanning laser thing. Scanning lasers are something I am very familiar with from my day job - although usually at the opposite end of the spectrum. Whilst the power of the laser is a big plus - I think there may be a problem. A scanning raster means the beam is only in one place at a time and only for an instant - as it is constantly moving. The beam gets its power (actually it's light energy per sqaure unit are) from the fact that it is so narrow. Using a dispersing lens to make the beam larger dissipates the same energy over a larger area so gains us nothing. The actual exposure would be dependant on the size of the laser beam, the size of the area it has to scan and the speed it is moving at.

What I'm wondering is this... My maths skills aren't good enough for me to work it out - but I've got a hunch that if you dispensed with the scanning and just enlarged the beam with a lens (excluding lens losses) so that it covered the negative - the exposure might be the same. I.e: the exposure is the same as any other lamp / bulb / light source covering the same area at the same distance, scanning or not. In this case, the only advantage the laser has is that it has fairly high power as a light source, but easier to dispense with the scanning raster and use a lens.

Am I right? Or am I talking none-sense?

 

[keithwms]

What I'm wondering is this... My maths skills aren't good enough for me to work it out - but I've got a hunch that if you dispensed with the scanning and just enlarged the beam with a lens (excluding lens losses) so that it covered the negative - the exposure might be the same.

Well, the variable to sort out is the raster rate, right? When rastering, you can "dwell" at a point as long as you like. So unless you specify that dwell time, we can't compare the exposures.

But your line of thinking is good: we could expand the beam from, say, a HeCd laser and probably get plenty of intensity over the size of a negative. I have a HeCd laser operating at 325 nm in my lab Expanders are a bit pricey, and you might need to throw away ~half of the energy putting the beam through a pinhole to get a nice Gaussian profile. That's the main issue with this, right? The Gaussian profile.... which translates into falloff in the print. You'd have to use a center filter or something if you wanted to get rid of that.

I am more worried about proximity effects when you raster, i.e. mixed doses from adjacent "pixels." Since flatbed scanners do work, I am sure this issue has been sorted out, but it's not obvious to me that re-photographing the neg with paper will automatically correct for this effect. I can think of some ways around this but they are a bit complicated.

Yeah, probably easier just to expand the beam And you get crazy intensities from a UV laser. I think I get something like a hundredth of the intensity from my D2 lamp, compared to the HeCd. I guess I get ~5mW from the HeCd.

 

[MattKing]

How are you going to "expand" the beam and keep it perpendicular to the negative?

 

[keithwms]

With a beam expander. 20x should do it.

 

[steven_e007]

Well, the variable to sort out is the raster rate, right? When rastering, you can "dwell" at a point as long as you like. So unless you specify that dwell time, we can't compare the exposures.

.

What I was thinking was.... whilst you dwell, you aren't exposing the rest of the paper.

My reasoning went something like this. Imagine you have a laser beam that is 1 cm by 1 cm and happens to be square (not very likely, I know - but for the sake of explanation).

Let us say you contact print a 4 x 4 cm neg onto a cyanotype.

So - our raster can go any way we like, but let say it goes top left, top right, bottom left, bottom right and back again. We can dwell as long as we like, lets say 1 minute in each of the four positions (again, not very realistic - but bare with me...).

If the cyanotype needs 30 mins, then the laser must dwell in each square for 30 mins, so the total scan time is 4 X 30 = 2 hours.

If we expand the beam by 2, the area increases by 2 squared, so the intensity per unit area is only 1/4 - so the cyano type takes four times as long i.e: 2 hours.

No, scale this up (and down) to a very small laser, a raster with dozens (or hundreds) of scan lines going at any speed you like, with or without dwell and... I think the same principle applies?