DIY ULF Lenses - 3D printing resin, epoxy casting or sand casting?

[Oslolens]

If a 56 inch lens covers the format you need a 10 inch aperture to get f5.6, and slightly bigger lens elements. The picture would be less sharp if a set of meniscus lenses are used.

Very few photographers need f5.6. If Avedon used f16 on 8x10" what would be the benefit of such a large and bright lens?

And are you looking in to a sharp lens or soft or very soft?

I just got my 138mm tubus mounted, it contains a 450mm f3.6 balopticon lens and is heavy and cumbersome.


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[Nodda Duma]

Such a lens can be designed of course, but the design form and thus the cost would depend on the focal length. The simplest/cheapest for a normal or portrait focal length would be a Cooke triplet type. At 10” diameter aperture, the glass itself would cost ~$8k-$10k. Mechanicals would be another $2k-$4k. NRE would be $2k-$4k.

So the answer is, no it wouldn’t break the laws of physics. Just your wallet.

[Havoc]

"Liquid optics"? Nothing new, Herschel used it in one of his telescopes. 2 halves filled with liquid in between. Different liquids give different indexes. But you can go large without needing massive blocks of materials.

[John Layton]

hey...what about that guy that creates lenses out of ice? Is he still doing this?

[Qeb]

Sorry for my slow reply

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Thanks Oslolens!

So, the emulsion will be very low/slow and I want to use constant lights instead of flash.
Thus I'm thinking I want the option to shorten my exposure time if needed.

Thanks for the photo upload!
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Hey Nodda Duma, Thanks so much for your reply also.

That's awesome great news that lenses can be custom made at these sizes.

I'm not sure about the focal length. I do have a ULF camera that I intend to use when I make more money for a new darkroom and bigger studio (currently using the dining room).

Would you be able to recommend a lens focal length for 1:1 portrait and focus at infinity? Sorry, for my ignorance.

Would you also know any companies that would make this lens?

Is a 20" diameter lens impossible?


Thank you for letting me pick you brain Sir!

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Be well everyone!

[Dan Fromm]

Would you be able to recommend a lens focal length for 1:1 portrait and focus at infinity?

Hmm. Getting 1:1 magnification at infinity needs a lens with an infinite focal length. You don't have infinite funds and the lens would be infinitely heavy. Are you sure that's what you meant?

What format is your ULF camera and what kind of portrait do you want to take? Focal length needed to fill the frame with a subject depends on film format and just what the subject is (face only, head and shoulders, ..., full body, full body + some surroundings).

Is a 20" diameter lens impossible?

Larger lenses have been made. Think refracting telescope. Also think about weight.

[Qeb]

Hey Dan Fromm,

Thanks for always chiming into my random posts :P :P :P

So, I'm getting I need two lenses, but I lack comprehension skills often.
(English is sort of my second language)

I noticed Richard Learoyd never does full body (full standing person) + surroundings.
What lens(es) (focal lengths and coverage) would I need to do half body but also full body at lets say 70"by70" (maximum).

I'm obviously dreaming a bit, but if my tech ideas are successful I might have the money to do all of this one day.
I mean I could get a lens or two now, but the lighting equipment and processors I need will be much much more than two custom lenses.

Sorry for this increasingly silly thread, I know people come here with similar goals.
But this is a long term dream and as I'm waiting on people with my tech ideas I thought I would use sometime to ask the hive mind some questions.

Thanks Dan and others

[Maris Rusis]

I am a sometime amateur astronomer and the subject of lenses has been fascinating.

Just for the record and just for interest large diameter lenses exist and the place where they are most often found is on the front of major refracting telescopes. It has been said with some truth that the cost of a lens and the difficulty of manufacture goes up according to the cube of the diameter. That's why there are so few really big optical quality lenses in the world.
A list of them is remarkably short:https://en.wikipedia.org/wiki/List_o...ing_telescopes

It's possible to buy a big lens today. A contemporary example could come from a maker like CFF Telescopes ( I have no commercial connection) who offer a 200mm f6.5 refractor. The price is about $27000 dollars and most of that is in the objective lens.
A even bigger CFF telescope has a 230mm lens working at f7 priced at about $37000.

If there was a simple and cheap work-around for the problem of fabricating optical quality giant lenses they would not be so rare. But very rare they are.

[Dan Fromm]

I noticed Richard Learoyd never does full body (full standing person) + surroundings.
What lens(es) (focal lengths and coverage) would I need to do half body but also full body at lets say 70"by70" (maximum).

760/14 Apo Ronar. And a lot of light.

He started out with a 1200/12.5 Apo-Saphir, found it too long. But he doesn't shoot 70" x 70".

[Nodda Duma]

Cost increases exponentially with diameter, so expect any build involving 20” refractive lenses - which would be near the upper limit — would be $100k - $250k as a very rough guess.