Making an UV enlarger

[Petrochemist]

Looks like the Kodak Enlarging Ektanon 10" f/4.5 will be exactly what I need, thanks!

380nm LEDs aren't nearly as expensive as the 365, and only a bit more than the 395, so I'll add that one to my parts list, thanks for that too!

Where did you source your fresnel lenses from? I found ones that would work at edmunds, but I'm wondering if there might be cheaper sources elsewhere.

There are loads of fresnel lenses on e-bay. I brought my 200mm f0.6 one from there

 

[Ethan Brossard]

There are loads of fresnel lenses on e-bay. I brought my 200mm f0.6 one from there

I couldn't find any large enough fresnel lenses on alibaba for less, but I didn't search much. I'll check out eBay as well, thanks!

I also looked a bit more at the lenses. The 10" f/4.5 ektanon does have one cemented group, but the 10" f/8 one does not. I'm guessing the cement won't block 1.3 stops of light, but I may get the f/8 version as well to test, as they aren't that expensive.

 

[Ethan Brossard]

Another question, for choosing fresnel focal lengths, what magnification should I use to determine the focal length I use for the lower condenser? My math shows that for a 2x enlargement with a 10" lens in my design, a 15.75" focal length is optimum, and for a 4x enlargement a 13.25" focal length is optimum. I've found both 13.8" focal length fresnels, and 18" fresnels. a 13.8" is closest, but would be shorter than optimum for the 2x enlargement. Would that have any adverse effects? I'm thinking I should go for the focal length best for the largest enlargement as when doing smaller enlargements the light will be higher per unit area, so the less optimum focal length will be counterbalanced by that. I'm also wondering about making sure there is enough distance between the fresnel and the negative to ensure the fresnel lines aren't in focus. The 18" fresnel could be 0.86" above the negative, while the 13.8" could be 0.66" above the negative.

 

[douwe]

When you set up your enlarger as a point source enlarger, the converging lens is fixed in relation to the enlarging lens. So you need to take the image distance (lens to negative distance) for the smallest magnification you want to print, and add some extra room for your negative carrier. Also, don't get your fresnel right on top of the negative: You don't want it in focus. For the largest magnification you want to print make sure the diameter of your condensor system covers the negative. The closer the negative moves towards your enlarger lens, the more coverage you need.

 

[Ethan Brossard]

dang, I wasn't thinking again. Remembering how my Beseler enlargers work, you're right. That'll mean I need a fresnel with around a 20 inch or 50 cm diameter any idea where I might be able to find one that large? This might make going back to diffusion a good idea, how much light do you think would be lost in a diffusion head?

edit: looks like Knight Optical has large enough ones, I'll do some redesigning of my enlarger head to match them

 

[douwe]

dang, I wasn't thinking again. Remembering how my Beseler enlargers work, you're right. That'll mean I need a fresnel with around a 20 inch or 50 cm diameter any idea where I might be able to find one that large? This might make going back to diffusion a good idea, how much light do you think would be lost in a diffusion head?

edit: looks like Knight Optical has large enough ones, I'll do some redesigning of my enlarger head to match them

So, based on my spreadsheet for this kind of thing (let me know if you want it) you could make an 8x10inch enlarger with:
- 240mm enlarger lens
- Two identical fresnel lenses of 365mm diameter and a focal length of 400mm

This ad gets close enough: https://www.aliexpress.com/item/32805855724.html
Scroll to the bottom: the have 380mm fresnels with a focal length of 450mm. Close enough I'd say

 

[douwe]

And that would give you a 2x minimum enlargement with enough room to spare.

 

[Ethan Brossard]

So, based on my spreadsheet for this kind of thing (let me know if you want it) you could make an 8x10inch enlarger with:
- 240mm enlarger lens
- Two identical fresnel lenses of 365mm diameter and a focal length of 400mm

This ad gets close enough: https://www.aliexpress.com/item/32805855724.html
Scroll to the bottom: the have 380mm fresnels with a focal length of 450mm. Close enough I'd say

Thanks!

Though Knight Optical, a company based in Britain, has 400mm diameter fresnels for $160, which looks to be the better deal. They also have a 400mm diameter one with a 275mm focal length which could be used for the upper collimating lens and reduce the size of the enlarger.
https://www.knightoptical.com/stock/default/lenses/fresnel-lenses.html?sap_clear_aperture_mm=400+dia

I'm also still thinking about a diffusion head. I was looking at diffusion materials, and came across holographic diffusers, which evenly diffuse light while maintaining 85% transmission efficiency at up to 80 degrees. I'm not sure yet how much one of those would cost, but using one of those in my diffusion head with both RGB and UV LEDs may be the less expensive option.

 

[Ethan Brossard]

Douwe: How did the non "s" componon work in comparison to the dialyte kodak enlarging ektar? I've found a fast dialyte that may work, but I realized this morning that I was calculating the angle of coverage based on longest side, not the diagonal, which requires a greater angle of coverage. It turns out I need ~57 degrees of coverage for a 240mm/9.5" lens, which a plasmat like the componon can manage, but will be beyond the range of a dialyte. Sadly I don't have the ceiling height required for a longer lens, so I'm thinking a 240mm uncoated componon may be best for me

 

[douwe]

Just an educated guess here: your exposure times might be 25-50% longer. Other than that it will be fine.

 

[Ethan Brossard]

Just read your article on Emulsive... great work!

For those of you that haven't seen it:
https://emulsive.org/articles/darkr...cyanotypewith-a-uv-enlarger-by-douwe-krooshof

 

[douwe]

Just read your article on Emulsive... great work!

For those of you that haven't seen it:
https://emulsive.org/articles/darkr...cyanotypewith-a-uv-enlarger-by-douwe-krooshof

Thanks Ethan! Now that I have a working enlarger, I'm really exploring how to use it well. Emulsive was kind enough to let me write an article about it.

 

[Ethan Brossard]

I'm making progress on my enlarger... the design is finished and I have a finalized parts list for it now. Before ordering all the components though, I wanted to do some tests to make sure the electronics would behave the way I want them to, so last week I built this test layout which is wired the same way the eventual enlarger will be, but with only 7 Blue LEDs, rather than the total 149 LEDs the head will have when finished (32 450nm blue, 32 530nm green, 31 660nm red, 54 395/385nm UV).

Here's a short video on what I've made so far:

 

[Mainecoonmaniac]

 

[MattKing]

Threads combined.

 

[Ethan Brossard]

An update on the enlarger I've been building. The enlarger itself is done I think, have to make a new negative carrier though

 

[radiant]

Two of my saltprints made with my UV enlarger from 135 negative were on display in gallery, see this video:

http://blog.vedos.tuu.fi/my-salt-prints-in-exhibition/

Next month those will be again on display in another exhibition. Quite a ride - and point is: very very very worth of the effort making the enlarger. Good things happen.

 

[ProfessorC1983]

My own UV enlarger project is coming along, currently consisting of a Century Graphic, El-Omegar 75mm/f3.5, condenser stage of an Omega B600, with 3D-printed negative carrier and lamphouse holding a 100W 395nm LED. I can get 8x10 salt prints from 3"x2" dry plate negatives in around 10 min exposure.

 

[pentaxuser]

What's interesting to me is that in the early days of this thread replies consisted of reasons why this just wasn't possible and this negativity lasted until 2021. Now we have a working example so what couldn't possibly be done is done

Is it just possible that there are lessons here for those whose ideas of what works and what doesn't or won't tend to be rather fixed

pentaxuser

 

[MattKing]

What's interesting to me is that in the early days of this thread replies consisted of reasons why this just wasn't possible and this negativity lasted until 2021. Now we have a working example so what couldn't possibly be done is done

Is it just possible that there are lessons here for those whose ideas of what works and what doesn't or won't tend to be rather fixed

pentaxuser

It is also possible that the availability of UV light sources at reasonable cost that produce heat amounts that are easily dealt with has changed a lot in ten years. In other words, what may have been either impossible, hugely impractical, or outrageously expensive in 2012 may have over time become possible, practical and reasonable in cost.

 

[cliveh]

The Sun, has a massive advantage over any UV enlarger.

 

[pentaxuser]

It is also possible that the availability of UV light sources at reasonable cost that produce heat amounts that are easily dealt with has changed a lot in ten years. In other words, what may have been either impossible, hugely impractical, or outrageously expensive in 2012 may have over time become possible, practical and reasonable in cost.

There's always a reason Matt. I just wonder if we occasionally respond with mindsets that are more fixed than is necessary with little qualification of why or what needs to change to make things possible.

In that vein are you Henry "there's always another side to the story"Fonda in the jury room to my Lee J Cobb character who is stubbornly cynical about human behaviour? I must admit that I tend to think of myself as E. G. Marshall who can be persuaded to change his mind if he has the truth demonstrated to him in a way that makes sense

pentaxuser

 

[douwe]

@pentaxuser, completely agree! Why not trust that there will be innovation and that impossible things will become possible? Keep an open mind and reason from first principles!

 

[calebarchie]

A little bump, interesting technology may be worth experimenting with for smaller stuff. Could try hack up a uv digital devere!

Kirin

Blank

kirin.hitry3d.com

 

[koraks]

Could try hack up a uv digital devere!

It would create a fascinating machine for sure!