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Ridiculous and totally crazy!
Lens: Insane 50mm Extension Camera: K7 
Posted By: Ouroboros, 07-18-2010, 01:49 AM

OK, I'm sure a couple of you out there may want to slap me for this but I wanted to find out how far I could extend macro tubes before the results were no longer usable.

I've asked on the forum before and many people were very helpful in providing me with the necessary equations to work out the magnification. I wanted to know what the real-world usable maximum was. So I got my scissors and tape, collected a bunch of toilet paper rolls and made the most stupid length tube I could, using my existing 50mm of tubes as mounts.

I know the construction sucks, they're not perfectly straight and there was light leaking in but screw it! I got the results I wanted and now I'll go buy the proper tubes for the length I want! The total length of my ridiculous construct is about 15 inches (mount to mount) and working distance from the lens was the same as usual at about 2 inches.

Here are the results!

In case you're wondering, those are my fingerprints! There is a slight blur because if you move even a micron, it shows.... You're heartbeat is enough to move you a micron.

The last shot is the mm of a ruler

Last edited by Ouroboros; 04-03-2011 at 08:36 PM.
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07-18-2010, 05:29 AM   #2
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A great feat of engineering you've made here, the effects you've got are impressive too.
I would seriously worry about dust and deposits getting into the camera and onto the sensor through the use of that cardboard tube though.
07-18-2010, 06:56 AM   #3
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Very cool! What is the magnification?
07-18-2010, 11:29 AM   #4
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i have a very silly question:
how do you focus and press the shutter while having your finger on the other end?

07-18-2010, 01:29 PM   #5
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#1. Yes, I was worried about dust inside the cam too so I made sure to tape most of the inside of the tube to minimize dust. I took a few shots with my normal lens on and it looks like I got away with it. The penalty of the tape inside was that it was shiny and light leaking made some shots cloudy.

#2. I use an online calculator and the magnification is around 7.5:1

#3. Heh heh, with difficulty! I had the cam on a table and I sat on the floor. The subjects were held in place using either a clamp or Blu-Tak, including my finger.
07-18-2010, 01:39 PM   #6
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That's very unusual. If you had asked me how those pictures were made I would have guessed a different method.
07-18-2010, 04:54 PM   #7
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Hmm those fingerprints match those found on the scene of a recent art theft...
07-18-2010, 05:53 PM   #8
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LOL I'm so busted now!

I'm tempted to buy another 4 or 5 sets of tubes and do this kind of stuff properly. I'm not going to use my card tube again, i don't need to risk dust getting in the camera.

07-18-2010, 06:03 PM   #9
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But what about lighting? I haven't had a great deal of experience but my impression is that tubes eat light big time. How did you light the subjects?
07-18-2010, 06:15 PM   #10
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For sure, lighting is a big issue here. The camera and lens need a great deal of support to keep everything steady because the exposure time is almost always going to be over a second. I had some good lighting just above the lens aimed at the subject. It's not too hard as the working distance was still about an inch or two, long exposure just means everything must be ultra still. Seems even a micron of movement means blurring.

Ideally I would have a wireless shutter remote and a couple of sweet remote flashes too, might be time to get onto B&H and check out the range.
07-19-2010, 04:07 AM   #11
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Two sets of fully extended bellows would work similarly with a little more control - cool that you could get such good microscope like images
07-19-2010, 05:56 AM   #12
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I think the way forward is to get the black PVC drain pipe and use it with a couple of caps, and a union.

If you get the pipe and a small section of larger pipe, or a pipe fitting (union) and bore it out to allow it to slide over the pipe it would let you then mount the tube and have a reasonable degree of freedom in terms of adjusting the coarse distance to subject and let you focus. The other option, and in hindsight perhaps the best would be to look at some of the PVC drain attachments, that allow the ipe to slide through and then with a large nut, compress a fitting on the outside, this would let the tube slide and be clamped. (i need to look at this as it has some possibilities. The caps, one for each end, would be drilled to accept the M42 lens thread at one end, and at the other, an M42-K mount flanged adaptor would be mounted.

This would allow the caps to be placed on any length tube you want and if you were to then mark the tube lengths, you could have a set of tubes for different magnifications.

You would also want to do 2 more things, very carefully. The first is to sand the interior of the tubes with about 600 grit paper, so they are rough and do not reflect light, this would reduce any internal reflections and help increase contrast.

The second would be to clean and wash the tube with mild soap, and then dry it. Mild soap would help get rid of any lingering particles of dust from the sanding process.

In measuring on my monitor the size of the MM ticks, and it is a shame you did not have this across or vertical, but diagonal, I estimate about 3.5mm is across the 23.5mm of the sensor, or a magnification of 6.7 :1 close but a little less than what you suggest.

Working distance will always be a little more than 2 inches for a simple reason.

As the length of extension increases, and magnification increases, you will be very quickly approaching the limit, which is always the lens focal length. at exactly the focal length of the lens you will have infinite magnification,
07-19-2010, 11:16 PM   #13
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Good points and ideas for constructing you own right there. I will just buy a few sets of tubes and screw em all together I think.

Something I will have to custom make will be a good support for the tubes as there will be a fair bit of weight on there! The old light box won't fit the bill here either, I'm gonna have to make a clamp that can hold the subject and have more lighting directed at the subject from above and just behind the lens.

I'm gonna order some gear tonight! I can't wait to see what results I can get from a better engineered setup!
07-20-2010, 03:12 AM   #14
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awesome! I like this kind of DIY projects, and it's great you get such good results. But isn't it quite possible to get to the 7:1 range by mounting a second lens backwards, rather than build a huge light tunnel? I think that would make for a more workable construction because it's less long.
07-20-2010, 03:37 AM   #15
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Now there's an idea... I wonder if I have the lenses necessary?

I was kind of liking how crazy this was, hey is it possible to have camera body--> extension tubes--> reversed lens--> extension tubes--> reversed lens?

I'm really pushing for absolutely insane here. Does anyone have the gear to try these combinations?

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