Tube lens / Variable Focus Assembly

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Craig Gerard
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Tube lens / Variable Focus Assembly

Post by Craig Gerard »

Here are a series of images showing various optical attachments of a tube lens assembly I have been working with and fine tuning over the past few months.

Initially, I wanted a low profile setup for use with infinity-corrected microscope objectives and their respective, dedicated tube lenses.

There were a few requirements i.e. some form of variable extension and manual focus capabilities (Unifoc 58 ), a facility to rotate the camera for changes to compositional orientation (Nikon PN-11), a rigid tube assembly that did not require additional support and fittings that had no 'play', 'tilt' or 'sag', etc.

The following images demonstrate the outcome:

Objective > Iris > Nikon MXA20696 tube lens inside SK housing > Schneider Kreuznach Unifoc 58 > Nikon PN-11 > Novoflex Nikon to EOS adapter.
Image

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Objective > Iris > SK Unifoc 12 > Nikon MXA20696 tube lens inside SK housing > Schneider Kreuznach Unifoc 58 > Nikon PN-11 > Novoflex Nikon to EOS adapter.
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Lens with M39 filter thread > 50mm M39 Canon extension tube> Schneider Kreuznach Unifoc 58 > Nikon PN-11> Novoflex Nikon to EOS adapter.
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Craig

*edit: removed some images
Last edited by Craig Gerard on Wed Apr 03, 2013 3:21 am, edited 2 times in total.
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Peter De Smidt
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Post by Peter De Smidt »

Interesting setups!

abpho
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Post by abpho »

Very clean and professional looking. You take awesome product shots.

canonian
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Post by canonian »

Optical Lego ;)

seta666
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Post by seta666 »

Beautiful set up, love the iris ;-) The nikon PK-11 is a nice adition and at lest in theory this kind of set up should have less centering issues than a bellows set up.

how does mitutoyo and nikon tube lenses compare to other options like morfanon? have you made any kind of tests?

Regards
Javier

Craig Gerard
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Post by Craig Gerard »

Javier wrote:how does mitutoyo and nikon tube lenses compare to other options like morfanon? have you mada any kind of tests?
Javier,
I have not done any exhaustive tests. I'm waiting until I've compared some high magnification results; but presently, between the Nikon and the Mitutoyo MT-1 dedicated tube lenses, I'm leaning toward the Nikon MXA.

I intend be more respectful of the morfanon based on the results uploaded to this forum and on Flickr. Next task is to house the morfanon in the assembly.



Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

seta666
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Post by seta666 »

Craig Gerard wrote:
Javier wrote: I intend be more respectful of the morfanon based on the results uploaded to this forum and on Flickr. Next task is to house the morfanon in the assembly.

Craig
The way I use the morfanon is inside cheap M42 tubes, you need to sand the middle tube a little bit first and then it makes a tight fit; the bigger tube hides the morfanon and the little one is not really needed, I use the M42 iris plus 2 rubber "O" rings to hold everything in place .
http://www.photomacrography.net/forum/v ... 7503#77503
You already visited this thread long time ago but just in case

One thing I found with the morfanon is contrast is a bit on the low side, I have just painted the inside of the morfanon (which is shiny black) with black matte nail polish (thanks soldevilla for the tip)


Could be also nice to take pictures focused to infinity with all three tube lenses, to see what happens to corner performance when used as normal lenses. The morfanon had awfull corner performance when used this way

What are in your opinion the pros/cons of this kind of set up compared to a more conventional bellows setup?

Regards
Javier

Craig Gerard
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Post by Craig Gerard »

Javier wrote:Could be also nice to take pictures focused to infinity with all three tube lenses, to see what happens to corner performance when used as normal lenses.
Javier,
I did do this with two of the 'tube' lenses and also a Rodenstock Apo-Gerogon 240mm.
http://www.photomacrography.net/forum/v ... hp?t=16723

The morfanon did not feature in that exercise. I do recall the image you took some time ago with the morfanon as a standalone lens.
Javier wrote:What are in your opinion the pros/cons of this kind of set up compared to a more conventional bellows setup?
Initially, it was to overcome cantilever concerns when using a bellows in combination with a StackShot rail on a vertical column; but the assembly has features that lend themselves to a number of setups (which I have recently completed). I still wanted to be able to vary the tube length a short distance in either direction from that designated in the tube lens' specifications, but I also wanted some form of manual focus capabilities.

I explored a number of different components whilst searching for a low profile arrangement, including a Nikon PB-5 with AS plate for the base. I also used an Olympus Telescopic Extension Tube, but the OM tripod collar was not well designed or robust enough and I wanted an accurate way of changing orientation of the camera. The next logical step was the Nikon PN-11 which is a superb piece but lacked any variable extension capabilities; this is where the Unifoc 58 entered the picture and from that point on I have not had a reason to look further; although special attention was required to ensure the bayonet fittings of the PN-11 did not permit alignment issues when coupled with non-Nikon gear. This was easily fixed in one instance with a gasket made from ProtoStar and a more costly (but worth every cent) solution applied at the camera end of the PN-11 (the blue bit should indicate what that adapter is 8) ). At the base of the PN-11 is an AS fitting made by RRS (the B5) which another member brought to my attention; it is specifically made for the PN-11.

In some of the images above I have included the Unifoc 12, this has less displacement than the Unifoc 58 but it is a very useful, though not essential, feature to have on the objective side of the tube lens.

Overall, the system performs like clockwork and is solid and stable from one end to the other.

I still use a bellows (have recently purchased a 'blue' one), and since the possibility of adding a stepper motor to a StackShot controlled linear translation stage has become a practical reality, as a consequence, most of my cantilever concerns have been addressed.


Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

RogelioMoreno
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Post by RogelioMoreno »

Beautiful setup!

The pictures are clean and clear. It would be nice to see Nikon vs Mitutoyo tube lens.

Rogelio

Craig Gerard
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Post by Craig Gerard »

Rogelio wrote:It would be nice to see Nikon vs Mitutoyo tube lens.
I'll be doing that over the course of the coming weeks.....months. I'm still finalising my new setup and it is currently taking most of my time and attention. I have been taking many single exposures and at this stage, if I had to choose between the MT-1 or the Nikon MXA, I would go with the Nikon; however, I have not begun to work at higher magnifications, the MT-1 may deliver some surprises when I begin such observations.

Here's another equipment image for height profile perspective comparison and general reference; plus I liked the image and wanted to include it in this thread. It currently has a Minolta Macro Bellows 100/4 attached. When using infinity-corrected microscope objectives I'm intending to use the Nikon MXA tube lens assembly, iris and Unifoc 12 with the bellows.

Image taken with a Canon 7D, Canon EF 70-200 L USM
Image


Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

crisarg
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Post by crisarg »

Very nice setups, I definitely see some other uses with the first one.

Thanks for the ideas. :)
Cristian Arghius

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typestar
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"Best" tube-lenses - your findings

Post by typestar »

Craig Gerard wrote:I did do this with two of the 'tube' lenses and also a Rodenstock Apo-Gerogon 240mm.
Dear Craig,
as far as I read here you tested all "official" tube-lenses (Nikon, Mitutoyo and also the newly discovered Thorlabs) and also the Rodenstock Apo-Gerogons. What I understood - you like the Nikon tube lens very much

1) As for today -- WHICH tubelens-combinations would you recommend?

2) What will be - with this tubelenses (or do they have different distances to watch) - the best distance = front of the tubelens to shoulder of the used (microscope-)lens ?
How "strong" and stiff fits the Nikon Tubelens (or the Thorlabs, does it have same size?) inside the Schneider 25 mm ring?

2) How performs the Apo-Gerogon 240mm in that setup?
Should I forget using this...?

3) Can you even provide us newer direct picture-comparisons?

Thankyou
for your efforts in advance,

Best wishes,

Christian
Last edited by typestar on Tue Apr 02, 2013 12:58 pm, edited 1 time in total.

Craig Gerard
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Location: Australia

Post by Craig Gerard »

Christian,

The process of testing the various tube lenses is currently being formulated by another member, his analysis will be far more educated than mine and no doubt will be presented in due time depending on his current workload; my recollection from recent comments is he was rather impressed by the Thorlabs ITL200.

The Nikon MXA20696 tube lens is very good. I am currently using a recently acquired Thorlabs ITL200 and have replaced the Nikon MXA in my assembly. Both of those tube lenses have similar dimensions and fit well inside the 25mm SK extension tube. The SK extension tube has an internal ledge upon which the front of the tube lens rests and is held in place by 'grub' screws present on the SK extension tube. The SK extension tube I'm using terminates in a 'V' mount; it was necessary to buy two V-Mount to M42 adapters for each end of the SK extension tube from Edmund Optics. The 'grub' screws on the second 'V' to M42 adapter are in direct contact with the exterior barrel of the tube lens. The 'grub' screws assist with alignment. Overall a rather expensive approach but an acceptable outcome with good internal alignment. The fitting is solid and firm and has not given me reason for concern.

Thorlabs sell a series of tubes specifically designed for use with the ITL200 and I expect that approach may be more cost-effective and more appropriate. I'd need to check on the specific part numbers of the Thorlabs tube system and compatibility with standard step rings.

I still use the assembly as presented in the images earlier in this thread but I no longer see a need for the Unifoc 12 because it does not offer any reasonable advantage in this arrangement. The Unifoc 58 and Nikon PN-11 combination work very well together with both components providing important contributions to the assembly.

I also use and have installed the Thorlabs ITL200 on my bellows. Focused at infinity, total distance from sensor to rear element of the tube lens was 140mm +-2mm. This is only a preliminary measurement and was not undertaken with any exact measurement intentions. I do intend to revisit this matter.

Your question regarding 'distance from objective shoulder to tube lens', this is a matter I have only briefly investigated but I do find that a distance of approximately 30mm is sufficient. Further input from other members in a separate thread (too much gear porn in this one) would be appreciated as up to now there has been no definitive demonstration or presentation regarding that particular matter. I'm yet to be convinced we have to adhere strictly to the suggested specifications...

I have not used the Apo-Gerogon 240mm to any extent. I was asked some time ago by a 'quiet reader' to use that lens on a FF camera but to date I have not undertaken the task (apologies); suffice to say, if you have the Apo-Gerogon 240mm keep it in your kit.


Hope this helps for now.


Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

ray_parkhurst
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Post by ray_parkhurst »

What is the reason for recommended distance between objective and tube lens front element? Is it for minimizing impact of reflections off the surface of the tube lens?

So far I have seen relatively little to refute that any decent tube lens will do, and distance between objective and tube lens is not critical. Do the "dedicated" tube lenses have good performance when used for infinity-focused regular photography? Is this a valid test to determine if your tube lens is good enough for the application?

I'm acutely interested in this topic since starting to test infinite objective performance...

rjlittlefield
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Post by rjlittlefield »

Craig Gerard wrote:process of testing the various tube lenses is currently being formulated by another member... and no doubt will be presented in due time depending on his current workload
That sounds like a delicate and gracious description of some stuff I've been doing. As a quick summary, I can say that the topic is unexpectedly complex, but most of the effects are pretty subtle. Differences between tube lenses are swamped by differences between objectives, and while the differences between tube lenses are definite, I have to look close to see them.
ray_parkhurst wrote:What is the reason for recommended distance between objective and tube lens front element? Is it for minimizing impact of reflections off the surface of the tube lens?
The main reason is to minimize aberrations away from center.

When the objective is placed very close to the tube lens, only the center of the tube lens gets used to form the entire image.

When there is separation between tube lens and objective, the center of the image is still formed by the center of the tube lens, but the corners of the image are formed by areas of the tube lens that get farther away from center as the separation increases.

You might expect that this would degrade the corners. But actually it can improve them, depending on gory details of the lens design.

The official tube lenses are formulated to minimize aberrations when used according to the manufacturer's recommendations. Deviating from the nominal separation will degrade the corners to some extent. However, the effect doesn't become obvious until the deviations become extreme. The Thorlabs ITL200 is specified as 70-170mm. Using it with zero separation would not be a good idea, but anywhere from 50 mm to wherever it vignettes would probably be fine.
Do the "dedicated" tube lenses have good performance when used for infinity-focused regular photography? Is this a valid test to determine if your tube lens is good enough for the application?
Yes to both, but it matters where you place the aperture. To run a valid test, you need to have an aperture that is the same diameter and placement as the rear of the objective you intend to use.

--Rik

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