Is there interest in retrofocus-optics for 4x5 5x7 Graflex from existing lens parts

[Dan Fromm]

just grab my Reflex-Primar 9x12, take the lens from the other camera, go outside for infinity (its night and weather is clear for the skyline). I hold the lens for infinity into the camera and the mirror works. That Graflex cameras need longer focus, I didnt know. 6 3/4 inch seems to be 171,45mm - the next focal length is a 168mm Dagor. I had never had a Grafelx reflex in my hands, please inform me about the normal used minimal focal length.

There were a number of 4x5 Graflex models. Depending on the model, the shortest original lenses focal lengths range from 6 3/8" to 10". 5x7 Graflexes came, depending on the model, with standard lenses from 8 1/2" to 10".

I don't know whether anyone has tried it, but one way to get a shorter than usual lens to focus on a Graflex is to remove the bellows and replace it with set of telescoping sliding boxes. I'm not sure how much this will gain, doing the job will ruin the camera for other uses.

I've tried a retrophoto lens on my 2x3 Speed Graphic, 1.75"/2.8 Elcan. It just covers 6x6, isn't that good a lens and absolutely can't be used on my 2x3 RB Ser. B.

Century Precision Optics, now a division of Schneider, made, probably still makes, afocal wide angle attachments for cine and TV cameras. I've used the Canon equivalent on several cine cameras, got terrible results on Nikkors for my Nikon SLRs. If I had to shoot with a wide angle lens on a Graflex SLR I'd talk things over with Century.

Good luck with your experiments. I don't mean to discourage you at all, you're trying to do something that's a little difficult.

[Nodda Duma]

What you post makes perfect sense from a design standpoint, balancing aberrations between the converter and base lens. I've seen that in many systems...Telescopes with focal reducers, Infrared zoom lends with afocal magnifiers and relays, etc.

Another benefit is that the magnitude of the aberrations are reduced when you scale the focal length by adding the corrector.

Nodda Duma wrote on 10-Feb-2015, 22:09 here in this forum :
edited the thread title to clarify this is a build-your-own-lens project.

Are you going to assemble it? Let me know how it goes.

[Dan Fromm]

What you post makes perfect sense from a design standpoint, balancing aberrations between the converter and base lens.

Yes, yes, yes but if the pieces of glass used are whatever's available this isn't guaranteed.

[ludwig]

Dan Fromm and Nodda Duma :

Thanks for datas. At first is my interest to collect informations about adapters - there is the cheap mass-market and the expensive market like Cine-Industry and Science/Astronomy. I reflect more on the cheap things, because they had been produced in thuch quantities, that for a reduced market like us largeformat (lf) the used-market-situation will stable for long time. This cheap things from the used-market can be categorized in groups, for what kind of lens they are better suited - this is just that I'm started. But now I have only 5 very different, 2 are in the region of 20-80$ (but the Olympus could be also new, than over 100$), the other 3 probably in the range 1-10$. I am sure, there will be 50-100 different forms exist, and of corse a lot of really nonsense, but who knows.

A problem in 4x5 Reflex is - wants the user to work with open stop, this would be difficult. If he wants to use stop down 22 (like Makiflex with a half-automatic stop) than I see a very good chance when the user accept a lens like Dagor starting f=6.8.

More simple it will be, if the user reflects on a kind of soft-focus, that was just a step in this direction I went, because my first thought after I noticed, there is something with this adapters, I take my 9x12 Primar-Reflex, put the 21cm Perscheid (Version not-color corrected) on it and the 0.65 Canon adapter. I thought for myself in an ironic form - Oh, with a softfocus-lens, you cannot go wrong, it cant become more worser (Sorry, dear lf-user in this forum, who loves the softfocus). But that was not the case, for soft-focus-user it looks interesting and I scratch my head. The next day, I used the worst lenses I have (I have never collected the "bad"-constructed, but by buying lots sometimes there are they). This had been the wide-angle aplanats, and my theoretical idea was true, their mistakes had now passed away. And you all know the dramas for a lf-er, when he wants to use a wide angle in 10x12 or 20x24", to get one is the problem, but there are a lot of wide angle aplanats. The lf-users are divided in two subgroups - the one wants professional quality, the other reflects on optical mistakes for aesthetical reasons. Perhaps are by the coming work of categorising the adapeters some forms, which are interesting for the non-professional quality,

And just this had been the starting point from me. I want to have some quality like Eidoscop 150mm in the area of stop 11-16, but equal over the whole field. Then there was the reflecting on an asphaer. I started with using the Zeiss Tele-Positiv 1:3 135mm, an unknown high speed landscape-lens in turned form. The feeling of an corrective was to look for a proprotionated front-part, after few minutes reflecting ( the mathematical meditation of a non-mathematican) I take the front-element of Apo-Tessar 1:9 30 cm. Because all of them could mounted at once together, I was pleased. It looks good, and thanks a long years ago prepared filtermount for Apo-Tessar I screw the Olympus adapter on it, the focus resulted ca 170mm. What I saw on the screen of my Kardan-Color 8x10 (The "Tank") on infinity was more, than I have ever thought on - no curvature of field and equal field for 18x24 cm (with vignetting near 8x10), neglectible distortion( 1 or 2 mm) and just this quality I thought for. I was neither happy nor melancholic, it was more a feeling of climbing in 8000meter Himalaya without oxygen - you have done the work, now back to earth.

Now Dan Fromm would say, the Tele-Positiv is to rare, thats correct, but I mention how the field of this lens looks like, and found two other possible candidats in other focal lengths, one is an unknown from my naked notmounted achromat-collection, the other is a early Balbreck landscape-lens.

Mr Beltrando writes me : "For your analytic trials, you can find patents of the early beginning of the cinema zooms, where the operators patented single lenses to make great opening retrofocus lenses with their usual anastigmats, and founding that the focal length differed with the distance of the lens. The results in black and white ortho were good enough for this purpose." He mentioned that the Nippon company Raynox sell such a single lens as a wide angle additive for numeric video cameras and that a Panasonic 0.7x converter (3 lenses) exist, which was very good up to f/2.8 and 80° aof, but very expensive.

[Nodda Duma]

Yes, yes, yes but if the pieces of glass used are whatever's available this isn't guaranteed.

The improvement will be lesser or greater depending on what's available. The threshold of acceptability depends on the definition of "good enough".

A methodical approach would be to characterize the aberrations in the lens subgroups being tested, and then it becomes obvious which combinations provide the best improvements. But I'm not sure of a way to do so within the reach of an amateur.

[ludwig]

Nodda Duma :

You write - A methodical approach would be to characterize the aberrations in the lens subgroups being tested.

This was once my ability, Zeiss ask me once in around 1990 to counter-proof their proofprojector for a specific lens.