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07-16-2014, 07:52 PM   #1
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Empty lens tubes

This thread topic may defy conventional forum categories...

Ok, I'm dabbling with an idea for a do-it-myself lens construction. Like so many projects, once I start making a list of all the obstacles and/or necessary parts I begin to feel the thing is hopeless because I don't even know where to begin. In this case, I'm struggling to figure out an effective way of holding lens elements in place. I'm hoping someone can suggest a viable solution in the form of either a pre-existing product or a re-purposed lens.

What I'm hoping to do more or less equates to a moderate telephoto lens in the realm of 100mm. The optical formula is relatively simple - at most, three elements in two groups, or possibly two achromats at opposing ends of the lens. Ideally, I would be using the three-element solution. The fact remains that no matter how many or few elements I'm using I still need a way to
  • Secure the elements
  • Allow for changing distances between elements to fine-tune the arrangement
  • Allow for a focusing method, possibly with the help of a helicoid mechanism
  • Have a way of inserting some kind of aperture, either through mechanical means or simple discs (paper, washers, etc.)

There are empty lens tubes available from certain companies (Thor Labs, for one) but these can be rather narrow because they are primarily meant for laser applications. It's tempting to go with one of these empty tubes because the companies also manufacture irises and aperture mechanisms with threading on both sides. This means two tubes can be combined with the aperture in the middle. Nevertheless, these things are all expensive just for the sake of an experiment, and it doesn't even take into account purchasing the glass itself (likely from Surplus Shed).

And speaking of Surplus Shed, I've scoured their site hoping for some kind of turn-key solution without much luck. I've considered trying to acquire a junk lens - the criteria for focusing and an aperture would be satisfied - however it would mean knowing how to properly disassemble the lens. I've taken a few apart and depending on brand, vintage, and seven other variables it's easy to mess up the aperture control or put the lens into an almost permanent state of tinker's parts. Another issue with the junk lens route is that it seems all lenses have elements of diminishing diameters as the construction gets closer to the camera mount. This isn't the end of the world, but for my experiment I'm trying to keep things consistent with elements of the same diameter. I'm actually trying to preserve certain kinds of optical defects, and with my scant knowledge of optics I haven't yet determined how differing element diameters impact the design.

Lastly, I am aware of a gentleman who runs the site JohnnyOptic.com - a relatively small site, but still useful in that he deftly summarizes some optical principals. The majority of his projects involve making lenses for the purposes of macro work. Most of these devices are a cobbling together of things through the use of empty filter rings. I may be forced to follow this path - convenient that the parts are readily available and plentiful - but it would involve creating a cylinder of many smal pieces. I've considered materials like PVC, but I have yet to find a method of successfully installing elements. Staying within the boundaries of photographic materials is useful because it means matching threads sizes, not needing to paint things black to avoid reflections, etc.

Any thoughts? Sorry to make it go on and on. Like I said, there's a lot to consider and I don't want to leave anything out that could later rule out an otherwise sound suggestion.

07-16-2014, 09:03 PM - 1 Like   #2
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The m42 lens Hanimar 135 f3.5 this is the same as the Photax 135mm f3.5, (rebadged) 10 dollars should secure a copy


This has 3 elements that all are forward of the aperture and are removed by unscrewing a single o ring from the front. Spacers all come out leaving the outer tube focus helicoil and aperture intact. Insert your elements with your own spacers and replace the o ring,




The m42 lens Helios 44 58mm f2 20 dollars should secure a copy


This has 6 elements 3 in front of the aperture and 3 behind. The rear 3 elements are held in a block which unscrews entirely leaving the aperture exposed, discard this.


The front 3 elements should be removable from the front by removal of o ring to allow reinsertion of your own elements and spacers. You will have to add extension tubes or a bellows to give correct focus.




The m42 lens Yashica Yashinon 50mm f1.7 20 dollars should secure a copy


The lens construction is exactly the same as the Helios, the 3 rear elements unscrew ina block leving the aperture exposed and all remaining elements in front removable from the front. Treat it exactly the same as the Helios.




I have not removed the front elements from the Helios or the Yashinon but they should free up and remove easily, I have removed the rear elements from both however and its a simple job.


I have removed all elements from the Hanimar/Photax and that's easier than the Helios or the Yashinon.


I would recommend re using old m42 lens bodies because they are very cheap and available, and come complete with aperture diaphragm and focus mechanism.


It is quite acceptable to have all elements in front of the aperture blades.


Hope this helps
07-16-2014, 09:40 PM   #3
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QuoteOriginally posted by Imageman Quote
The m42 lens Hanimar 135 f3.5 this is the same as the Photax 135mm f3.5, (rebadged) 10 dollars should secure a copy
...and so-forth...

Wow, this is nice wealth of information to start with. Thank you! I wasn't expecting the average forum member to know the exact optical formulas on any given lens (although the Russian lenses have been around long enough they are bound to be taken apart and studied). The Hanimar is a nice candidate because of its large element sizes. What I'm hoping to do might be best served by the aperture located in the middle, though. I'm going off of some existing drawings, so I'm reluctant to stray from them as far as moving components around. Still, the lens design software I have might prove useful in learning how this re-arrangement will play out.

The Helios could work for the reasons above, although I can't do the math off the top of my head to figure out the element focal lengths necessary to secure the effective focal length of the lens on something as physically short as the Helios.

As I said, I have some lens design software, WinLens which has some example lens plans. I've learned a surprising amount about the interface in a relatively short period of time. If anything, it's only re-affirmed my instinct to explore my options before starting something and then be forced to start over completely.

Thank you for your suggestions!
07-17-2014, 05:19 AM   #4
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I hope you're aware that a 3 element lens is going to be crap. Had a 135/2.8, was shit, took it apart (EDIT: managed to pry out the last element).
I actually have the same question as you do, so I'll be following this thread. I suggest you search the forum for the "TP special" and the TC special".


Last edited by Giklab; 01-27-2015 at 08:57 AM.
07-17-2014, 05:41 AM   #5
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What I would do would be to get macro extension tubes and fill them with the glass. Focus would be difficult to obtain then however.

As for holding optical elements in place, use baffles/spacers between them.

That being said, optical design is a pretty complicated science/art. Don't be disappointed if your first attempt is full of aberrations and hardly sharp...

You could use the educational version of a program such as OSLO to try and learn how the different elements (thickness, curvature, index of refraction, distance) play together. You can even load a 50mm doublet and a few telescope designs to see how it's done.

QuoteOriginally posted by LowVoltage Quote
know the exact optical formulas on any given lens
With all due respect, that's not the same as knowing the exact optical formula of the lens design. That's knowing how many optical elements there are. Useful but a far cry from being able to duplicate the lens.

There are hundreds of glass types available for lens designers to use, each with their own properties and characteristics. Again, OSLO has an interesting (if basic) catalog of such glass, organized by manufacturers (Schott, Corning, Hoya, etc). Even small differences in the refractive index will influence the final result, especially regarding aberrations (which, when poorly controlled, can make or break an image).

It might come a time when you find out that you need to polish a lens element to get the curvature you want. Astronomy clubs can maybe help you with this, many astronomers polish their own mirrors.

I'm not trying to be pessimistic here, but I wouldn't want you to dive in without knowing a little better what you're getting into. I have a 450-pages book called "Basics of optical engineering"
07-17-2014, 06:46 AM   #6
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I would recommend as initial investments, bellows and a sturdy tripod with a quick release.
The bellows sets you free from the camera register, solves the fine focus problem and allows , via a suitable adaptor, the freedom to concentrate on your lens experiments
The quick release will save a lot of time with experiments.

I tried a lens bench but don't think it is worth the trouble because it does not allow test photos.

I have my hobby lathe set up with gears and tooling for various metric and inch camera threads for medium format camera building.
In photo below, I have adapted a simple Rodenstock enlarger lens with the Leica M39 thread to the bellows K adaptor using the K mount from a dead lens
I recently enjoyed making a similar adaptor for PF member 6BQ5 , so if you get stuck finding threaded adaptors, send me a pm.

For the first lens you could try a simple meniscus portrait lens of about 75 ~ 100mm
Over on apug, a member has just posted some delightful portraits from a plastic meniscus and a spaghetti measure as a diaphragm.

For a more complex lens, i would suggest a symmetrical lens based on obtainable achromats.
You can model first. Prescriptions are rare but there are some, again search apug.
The advantage of the double gauss is that it has a generic prescription, available on internet that can be multiplied linearly to any focal length.
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07-17-2014, 10:56 AM   #7
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QuoteOriginally posted by Giklab Quote
I hope you're aware that a 3 element lens is going to be crap. Had a 135/2.8, was shit, took it apart (Well, almost. The front element won't budge, I'll probably just have to dremel it out).
I actually have the same question as you do, so I'll be following this thread. I suggest you search the forum for the "TP special" and the TC special".
Yes, in fact I'm counting on it to be crap!

07-17-2014, 11:39 AM   #8
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Theres nothing wrong with 3 element lenses.


By this line of reasoning a single element lens is worthless, and a 50 element lens is the best you can get.


Many of the best lenses ever made are 3 or 4 or 6 elements. Its about aberrations its about resolution its about rendering its about contrast, and the mix the lens offers.


A Tessar is one of the best lenses you can own, and that's a 4 element lens, and its constructed like and behaves like a 3 element lens.


A Biotar or a Planar has 6 elements, are they inferior to a 10 element Soligor? No they are not.


Speaking personally, I have several 3 element lenses, theyr the best lenses I own.


My best lens has 3 elements.


My sharpest lens has 6 elements.


My weakest lens has 15 elements.
07-17-2014, 11:39 AM   #9
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QuoteOriginally posted by bdery Quote
What I would do would be to get macro extension tubes and fill them with the glass. Focus would be difficult to obtain then however.

As for holding optical elements in place, use baffles/spacers between them.
If I were to go with the extension tube route there is certainly something to be said about the flexibility of M42-based items. The helicoid mechanisms I mentioned in the original post used M42 threads and, oddly enough, have a 52mm filter thread at the other end. This is just one example of how a piece of hardware starts out looking perfect and then a curve ball creates a whole set of other considerations.

Any comment on the particulars of finding/identifying baffles and spacers? I've tried looking up such items, but even putting them in the context of optics or lens elements doesn't get me anywhere on Google as far as securing a supply. Taking apart old lenses is all well and good, but that's not where I'm planning on getting the glass, so I can't expect to find spacers for the diameters I plan on using.

QuoteOriginally posted by bdery Quote
With all due respect, that's not the same as knowing the exact optical formula of the lens design. That's knowing how many optical elements there are. Useful but a far cry from being able to duplicate the lens.
Oh yes, I know the design is only part of it. What I meant regarding "knowing the exact optical formula" was I don't expect 99% of users to know what is inside their lenses, let alone how many elements in how many groups. Having a member explicitly say there are x-number of locations in a junk lens to put elements is helpful to the extent that I know what housing has more options. Of course, that doesn't guarantee success!

WinLens3D includes a catalog of glass available from the guys like Hoya, et al. and interchanging elements of otherwise matching diameters, focal lengths, and thicknesses make the (numerous) aberration and refraction index graphs change, some times drastically. I will have to check out OSLO. I'm surprised it didn't show up when I was first looking. My Youtube advertisements seem to now be exclusively for Zemax...

Like an electrical circuit experiment, I need something to build on - my proverbial "optical breadboard". For once I'm trying not to be a perfectionist and just do something to see if it works. Once I've determined something falls between the extremes of "complete disaster" and "complete success" then I can start trying alternatives. Nevertheless, I'm trying to be smart about the foundations of this entire enterprise. For example, I'm sure as hell not using cardboard as my lens tube because, for one, I'm not keen on inviting that level of debris into my DSLR's sensor!
07-17-2014, 09:35 PM   #10
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QuoteOriginally posted by wombat2go Quote
I would recommend as initial investments, bellows and a sturdy tripod with a quick release.
The bellows sets you free from the camera register, solves the fine focus problem and allows , via a suitable adaptor, the freedom to concentrate on your lens experiments
The quick release will save a lot of time with experiments.
The bellows option is very, very attractive for the precise reasons you mentioned - focus and camera register. The math I'm doing results in some constructions that have back focal lengths of around 100mm. I'm not sure what most bellows have as the minimum extension (I think 40mm is one quote I read), but I believe it would actually put my Frankenstein's Monster closer than necessary; obviously, I can then "focus-through" the necessary distance for infinity-focus and go longer for closer shots. The other thing about bellows I need to check out is the ability to rotate the camera to the portrait orientation. The PF reviews mention this option for at least one of the M42 versions, but nothing is said about the K-mount ones. My only other caveat is bulk and weight of the bellows. Ideally I would be able to move around without messing with a tripod. Not being able to shoot vertically isn't the end of the world - this would be a full-time manual focus contraption, so slowing things down with a tripod, shooting in landscape mode might actually do me some good. I would probably crop things down to squares. And I like squares!

The helicoid units I mentioned earlier would do well to replace the bellows. My only gripe there is even the cheapest ones cost at least what a used bellows goes for. I suppose I'm asking for too much, but I'm hoping to have a good range of focus. (The bellows range would be more than enough!) The helicoids vary in base extension and some only have a range of 5mm, others are more like 25mm. Predictably, the prices increase with the range.

QuoteOriginally posted by wombat2go Quote
For the first lens you could try a simple meniscus portrait lens of about 75 ~ 100mm
Over on apug, a member has just posted some delightful portraits from a plastic meniscus and a spaghetti measure as a diaphragm.

For a more complex lens, i would suggest a symmetrical lens based on obtainable achromats.
You can model first. Prescriptions are rare but there are some, again search apug.
The advantage of the double gauss is that it has a generic prescription, available on internet that can be multiplied linearly to any focal length.
This is actually what I'm aiming for. I'd like to skip the single-element test (I'm impatient) and go straight to the multi-element experiment if I can. Without going into all the details, I might go with two achromats depending on a few factors. An effective focal length for the entire setup would be between 85mm and 100mm, maybe a little longer if necessary.
07-18-2014, 05:29 AM   #11
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QuoteOriginally posted by LowVoltage Quote
Any comment on the particulars of finding/identifying baffles and spacers? I've tried looking up such items, but even putting them in the context of optics or lens elements doesn't get me anywhere on Google as far as securing a supply. Taking apart old lenses is all well and good, but that's not where I'm planning on getting the glass, so I can't expect to find spacers for the diameters I plan on using.
Not really, no. Maybe hardware stores would have something that would work. But I doubt you'll find anything by searching for "optical baffles". You'll have to repurpose something else. Maybe o-rings would work, metal ones maybe? Vacuum systems often use coppers o-rings and that could be a good place to start.

QuoteOriginally posted by LowVoltage Quote
Oh yes, I know the design is only part of it. What I meant regarding "knowing the exact optical formula" was I don't expect 99% of users to know what is inside their lenses, let alone how many elements in how many groups. Having a member explicitly say there are x-number of locations in a junk lens to put elements is helpful to the extent that I know what housing has more options. Of course, that doesn't guarantee success!
If you're interested in general info, number of elements, etc, look at "The Pentax Page" (google it) and you'll find that info for every Pentax lens ever made. There are often basic drawings included.

QuoteOriginally posted by LowVoltage Quote
I will have to check out OSLO. I'm surprised it didn't show up when I was first looking. My Youtube advertisements seem to now be exclusively for Zemax
Zemax is much more mainstream, OSLO's interest is the free version.
07-18-2014, 06:21 AM   #12
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QuoteOriginally posted by LowVoltage Quote
The other thing about bellows I need to check out is the ability to rotate the camera to the portrait orientation. The PF reviews mention this option for at least one of the M42 versions, but nothing is said about the K-mount ones. My only other caveat is bulk and weight of the bellows.
Both the Pentax K-01 and the Pentax ist-sd fit in the Pentax Auto bellows -M in landscape and protrait orientation.

The Bellows-M is easily hand hold-able.
Herbert Keppler, back in the Ashai-Pentax days, said " ..There are a number of photographers who use the bellows units and Bellows Takumar as their all-in one flexible camera unit for all photographs."
07-18-2014, 07:51 PM   #13
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QuoteOriginally posted by bdery Quote
Not really, no. Maybe hardware stores would have something that would work. But I doubt you'll find anything by searching for "optical baffles". You'll have to repurpose something else. Maybe o-rings would work, metal ones maybe? Vacuum systems often use coppers o-rings and that could be a good place to start.
Yes, I'm hoping I can find something like this to help me keep things centered as best as possible. Home Depot will be seeing me this weekend, maybe Acme Vacuum, too!

QuoteOriginally posted by bdery Quote
If you're interested in general info, number of elements, etc, look at "The Pentax Page" (google it) and you'll find that info for every Pentax lens ever made. There are often basic drawings included.
Thanks, I'll check that out... if you're talking about Bojidar Dimitrov's site, then I'm already aware. Somebody give that guy a medal - a lot of good info there, indeed.

---------- Post added 07-18-2014 at 11:09 PM ----------

QuoteOriginally posted by wombat2go Quote
Both the Pentax K-01 and the Pentax ist-sd fit in the Pentax Auto bellows -M in landscape and protrait orientation.

The Bellows-M is easily hand hold-able.
Thanks, a quick search showed it's got a single rail. Most seem to have two rails, so this one would be a lot lighter. I'll keep an eye open for this.
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