Close-Up lenses for LF photography, advice needed

[Bob Salomon]

OP here... Sorry if I wasn't 100% clear in my OP. I was interested in using close up lenses for soft-focus photography. I presently have a 300mm H=6.8 Rodenstock Imagon with no discs/"strainers"/insertable grids in a No. 3 Copal shutter. The image it projects is good but find that it stays unused in the cabinet. Was looking to replace its rear elements with 58mm (I believe to be the rear thread of the shutter) close-up lenses and see what I could get. I was looking for advice on where to start.

The Imagon only has a lens cell behind the shutter. What do you plan on replacing?

[Mark Sawyer]

It's my understanding the Imagon is just that, a close-up diopter, please correct me if I am wrong.

I suppose you could use the Imagon as a close-up diopter, just as you could use any positive single-celled lens (front of a Petzval, rear of a Tessar or Verito, half a Rapid Rectilinear...) as a close-up diopter, though the results likely wouldn't be optimum.

Pictorialist photographer Heinrich Kuehn/Kühn, along with the designers at Rodenstock, formulated the Imagon in the 1920's specifically because he wasn't satisfied with other soft-focus lenses of the time, many of which were achromatic doublets. Based on that, I think the Imagon was more than just another close-up diopter.

[Oslolens]

The Imagon only has a lens cell behind the shutter. What do you plan on replacing?

Do you know if there is threads on the front of the shutter?

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[Greg]

Do you know if there is threads on the front of the shutter?

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There is a threaded ring with "300mm H=6.8 Rodenstock Imagon" and a serial number marked on it.

[Bob Salomon]

There is a threaded ring with "300mm H=6.8 Rodenstock Imagon" and a serial number marked on it.

That ring unscrews and then you will have the shutter’s front threads.

[xkaes]

OP here... Sorry if I wasn't 100% clear in my OP. I was interested in using close up lenses for soft-focus photography. I presently have a 300mm H=6.8 Rodenstock Imagon with no discs/"strainers"/insertable grids in a No. 3 Copal shutter. The image it projects is good but find that it stays unused in the cabinet. Was looking to replace its rear elements with 58mm (I believe to be the rear thread of the shutter) close-up lenses and see what I could get. I was looking for advice on where to start.

Thanks for the clarification. As mentioned, the Imagon lenses -- they made a 200mm, 250mm and 300mm -- were two element lenses with the glass behind the iris. Basically a supplementary close-up lens with a shutter and diaphragm. You can do the same thing with any shutter and supplementary close-up lens -- and the glass can be on the front or the rear of the shutter. And, if you want, you can place one supplementary close-up lens on the front of the shutter and another supplementary close-up lens on the rear -- the two together basically shorten the focal length of the other -- and shrink the image circle at the same time.

One thing, that has been mentioned, is the need for an adapter to connect the supplementary close-up lens(es) to the shutter -- the adapter has to have a longer than normal thread to reach into most shutters. The thread on the supplementary close-up lens by itself won't reach -- and it will undoubtedly be the wrong diameter anyway.

The other point to mention is that with two supplementary close-up lenses used in combination, the results change with the distance between the two supplementary close-up lenses. Perhaps someone has a formula to estimate the change -- or can provide an explanation. You can use Gullstrand's equation as a starting point.

[Greg]

You will also find achromatic lenses or lookalike as the back cell of some lenses, like my 12 inch Wollensak f4,5 is ca 200mm f3.

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Thanks,
My 12" f/4.5 Velostigmat was my first lens for my 8x10. Looking forward to try the back cell on my whole plate this weekend
Greg