Lens diopters for the complete idiot (me)

[Jac@stafford.net]

My situation - I built a low altitude aerial camera based upon a Zeiss 75mm lens. It is superlative with fixed focus at infinity. Very cool. Now I would like to bring its use to earth with just a few fixed focus distances.

It is convenient that it accepts 138mm filters which are rather common in cine applications. Cine photographers are technically astute so I am thinking of getting one or two diopter lenses, or how many it requires to do some land-level images. (Sure there may be image compromises but I'm good with that in LF.)

Sorry for so many words when my question is: what numerical diopter strengths do I need to bring this wide-angle 75mm to focus at specific distances such as 3', 15', 50' and so-forth?

186570

[Havoc]

Can't help with the diopeters, but that camera is a nice piece of work.

[Maris Rusis]

Dioptres are just the reciprocal of the focal length expressed in metres. So a 1 dioptre lens added to a lens with a fixed infinity focus will get you focus at 1 metre, a 0.5 dioptre lens moves focus to 2 metres, 0.25 dioptre lens brings 4 metres into focus, and so on ....

[Leigh]

Hyperfocal distance at f/16 is 62 feet, with focus from 31 feet to infinity.

Do you need to focus closer?

- Leigh

[ic-racer]

Just a guess, that the large 'Cine' diopter lenses will cost more than the camera (link to tiny Bolex diopter that won't fit your camera for $450 (https://www.ebay.com/itm/Kern-Aspheron-6-5mm-wide-adapter-for-Bolex-H16-12-5-100mm-vario-switar-/132456726318)). If you do go that route, diopter math was made to be easy (addition and subtraction). Convert your 75mm lens to diopters (13 diopters)

For very little money I'd make some graded focus shims, maybe different colors. Place between the lens mount and camera body.

Do you have a ground-glass option? I don't have a 75mm that fully covers 4x5", but when I do use it, focus needs to be prefect otherwise the pictures are out of focus.

186572

[Mark Sawyer]

We could go through the math of diopters being additive and your 75mm lens being a 13.333 diopter plus the +2 diopter added to give a 15.333 or 65.2mm lens but finding the focal distance gets into lens thicknesses and nodal points that move around when you add the diopter lens...

Best to buy a cheap set of diopters and see what they do. Better yet, make a set of extension tubes...

[Drew Bedo]

Umm . . .The TravelWide accepts several 90mm lenses, is rigged with no bellows, and could be an aerial camera. It also has a focusing helical mount which allows for focusing at less than infinity.

Its pretty cheap too.

[Dan Fromm]

Drew, Jac's lens is a 75/4.5 Biogon. It is a gross heavy mostrosity probably not suitable for a Travelwide.

The lens is quite usable on a conventional 4x5 monorail -- it was sold for that application -- but for some reason Jac doesn't want to do that. He's trying to modify a clever solution to one problem (aerial photography of distant subjects) for a rather more general problem (photography at closer distances). Could be that his starting point (that clever solution) is preventing him from seeing the obvious. Could also be that he wants a simple relatively compact fixed focus camera for near subjects.

Putting shims between lens and camera body, as has already been suggested, seems the best way for Jac to get what he says he wants. I like the monorail solution better, but that's my preferences speaking, not his.

[Jac@stafford.net]

Drew, Jac's lens is a 75/4.5 Biogon. It is a gross heavy mostrosity probably not suitable for a Travelwide.

The lens is quite usable on a conventional 4x5 monorail

I already have tripod-mountable cameras for 75mm (or 3" Pacific Optical (PO)).

186607 ... and w/o bellows ... 186609

An interesting thing about this PO version is that the rear element is larger than the 4" dimension of the film plane. It covers 5x5"

186608

And I have other builds, mostly strange.

Thank you to all who answered my original question.

[ic-racer]

You have a couple of great cameras!

[Greg]

In the 1980s, had a chance to use a Zeiss-TECHNIKA-Biogon on a 4x5 Super TECHNIKA (hope my nomenclature is correct) to take some hand held architectural images. If I remember, was a challenge just to get the "rig" together, but I can't remember why. Camera was heavy and awkward to carry up a vertical metal ladder inside the top floor of the building where all the utilities were located. Had to squeeze through some tight spaces and dodge a fair number of pipes just to get to the ladder, and then at the top of the ladder had to lock my legs around the ladder to unlatch the overhead door's handle and open it, thank God for wearing a headlight. Getting down was more challenging that getting up. Swore never to do that again until I got the Chromes back from the lab. They were amazing. Client was totally impressed with the images. Some years later had the chance to acquire that same optic at a great price, but for some reason didn't... regretted it years later and even today. Jac, good luck with your project. Sounds like it will be well worth it in the end.

[Jac@stafford.net]

In the 1980s, had a chance to use a Zeiss-TECHNIKA-Biogon on a 4x5 Super TECHNIKA.

Good for you! I find the Super Technika w/75mm Biogon well balanced - with both left and right grips, something unattainable then and today. Being heights adverse I admire your effort! I get shivers just imagining.

[Jac@stafford.net]

Another odd-bird. A 47mm ƒ5.6 S/A fitted to a universal 4x5 back which, of course, accepts many roll film backs.

186668 and what started this nonsense, my first 47mm ƒ5,6 on a handmade wood body. 186669

Of course each has a focus helix and ground glass back

[Fr. Mark]

I have some diopters that I've used with 35mm film as close up lenses on a 50mm lens. I've also used them in front of a Sinar Shutter on 4x5 or 5x7 to see what they'd do in comparison to plasmats. They are very soft focus. I've never tried them in front of a plasmat so I don't know how they'd degrade the performance. Those diopters/meniscus lenses have huge coverage used as the only lens, way beyond 8x10. I was given an iris from a stage light which is bigger than I need. I worked out an f stop scale for it, put a UV filter with the same thread diamter as the diopters and now can have a variety of focal length soft focus lenses for my restored 8x10. I plan to mainly use "better" lenses though. it never occurred to me to use them in front of the better lenses. I will have to try that, I suppose, if only just to see what it looks like on the ground glass.

[coisasdavida]

such as 3', 15', 50' and so-forth

3' would be close to 1 meter, so +1 diopter
15' would be close to 5 meters, so +0.2 diopter
50' would be close to 15 meters, do +0.07 dioter

+1 would be very easy to find, +0.25 could be a reading glass lens, +0.07 have no idea

[Fr. Mark]

The so-called close-up filters are diopters. I have a set referred to above +1, 2, & 4. They can be used in combinations. These are positive meniscus lenses. I’ve used them to take 5x7’s. The coverage for these are huge as taking lenses. Way beyond 8x10. I put the 1 diopter in a piece of cardboard in an otherwise blacked out 2nd story bathroom window once and it illuminated a vast area out focus. I got a whiteboard to see what it looked like in focus—-I couldn’t move the opposite wall and it covered that. Iirc it was 30x48”. Someone will have a link to the guy selling meniscus lenses for ULF work at a sensible price.

[Maris Rusis]

Variable dioptre lenses are easy. Just get two of the same power but of opposite sign eg a +3 and a -3. Standard 75 diameter mm spectacle lenses are a good place to start experimenting. When the lenses are placed in contact the powers cancel and the result is 0 dioptres. When separated by 1 millimetre the power becomes 0.009 dioptres. By varying the spacing other powers can easily be generated. Gullstrand's Equation says it all. But that does not solve the OP's problem needing huge and unobtainable (?) dioptre lenses.