Tube lens setup without adjustment

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JKT
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Tube lens setup without adjustment

Post by JKT »

I suppose there are two main philosophies to set up your tube lenses. The first minimizes the number of required parts and the second the adjustments when changing lenses. I prefer the latter. The tube lenses are nothing special, but they work for me.

The first part of the setup uses Thorlabs 3" SM2 tube, 2 clamps and Hejnar plate as base. At one end of the tube is RAF adapter for Canon EOS and at the other Thorlabs SM2 to 52mm adapter. All the others screw on that adapter. No further adjustment required ... anymore. Some measurements and calculations were required in setting this up 8) and in some cases the tubes and rings likely cost more than the optical part. Two are missing from the portrait: S-K C 240, which doesnt' have all the tubes yet and DCR-5320 Pro, which is still in transit. After that I think I'm done. ...or maybe not. Depending on on the performance of that 240, I might be tempted to test stacking two +2 diopter lenses. That would be either another 5320 or Century Optics, if my memory is correct and +2 is available. All the microscope adapters use T2 at the other end, so DCR 150/250 and Canon 250D have that at the end. Short focusing DCR150 is easy by removing 14mm or 28mm tubes.
YOptics 1 - long (201003).jpg
3000x2000

The second part uses RAF adapter from EOS to 58mm and adds 58mm to 52mm StepDown to it for permanent 52mm attachment. As in the long setup, the lenses screw on that without need for adjustment. In practice only the longest is currently useful as I use FF camera. The middle one might be useful with APS-C and the short one would require m4/3. Makro Varon or similar would be a nice addition. :wink:
YOptics 2 - short (201003).jpg
3000x2000

What you may or may not notice is that most of the setups include carefully measured plastic spacer, which finalizes the extension. The length is likely more accurate than my capability to measure what the length SHOULD be.

Oh well - mostly I just wanted to show the pictures. :D

Lou Jost
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Re: Tube lens setup without adjustment

Post by Lou Jost »

A nice collection! Are you going to attach reversed lenses to them, or objectives?

May I "stir the pot"? You should try some medium format lenses too. Since you would only use the center of the medium format image (unless you buy a shift adapter), they provide the most uniform resolution across the frame, if that is important to your application. I suppose some of your SK lenses could be considered medium format.

The nice thing about using camera lenses rather than diopters and bellows lenses is that they let you skip the tubes and spacers completely.

JKT
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Re: Tube lens setup without adjustment

Post by JKT »

So far I have used them with objectives. With the coming two additions I may finally have the longer end covered sufficiently. That leaves magnifications 3.5 ... 7.5 as problematic area. MP-E works for 3.5 ... 5 and it is definitely enough for me under 3x, but a bit more resolution near 5x wouldn't hurt. And then something between that and 7.5x would be nice as well.

I intend to try stacking, but I don't have 28 or 35mm S-K Componons. I have 40mm Apo Componon, and I'll test that eventually with the longer tubes. I have also S-K C-S 50/2.8, but there seems to be something wrong with it. A Mitutoyo 5x would be an easy one, but I wonder what kind of sharp image circle it has. It might give the 6x (240mm) and 6.25x (250mm), but would it give enough for 5.25 (210mm)? I'd like to have the corners at least reasonably sharp on FF.

I've never played with medium format, so I have no idea what to look for or what even exists. For stacked lenses they might be useful, but I suspect that with microscope objective they wouldn't help. The image circle of the objective is the problem. On second thought, something in the range of 280 ... 300 mm might be useful. Has anyone tested Canon EF 300mm f/4.0 L IS USM on full frame? It would have dual use if it worked with microscope objectives as well. Shorter ones don't work - at least not the ones I have. There is always vignetting.


Edit: I forgot to mention that these were done with Canon EOS RP and EF 100mm f/2.8 IS L Macro at f/8 and minimum step at the automatic focus bracketing. Worked like a charm!

Lou Jost
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Re: Tube lens setup without adjustment

Post by Lou Jost »

I've tried the Canon 300mm 2.8 fluorite with objectives. Though it looks ridiculous, it works, but at least in my combo, there was a bit of red CA so I have preferred other options.

JKT
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Re: Tube lens setup without adjustment

Post by JKT »

That's FD, isn't it? Couple of decades of development might help against the CA. Then again - it might not. :) More important is the f/2.8. I was thinking about f/4.0, which would keep the price reasonable. Unfortunately the vignetting behaviour is unknown.

Edit: Apparently there is also EF Fluorite. I didn't know about that one.

Lou Jost
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Re: Tube lens setup without adjustment

Post by Lou Jost »

Yes, the 300 2.8 has a long history. Mine is an FD which is the cheapest, but it is still superb, breathtaking really, with almost no CA in ordinary use, even with pixel-shifting. Don't know why it wasn't so good as a tube lens. I should probably play more with it.

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