Extreme extension tube.

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All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

Extreme extension tube.

Post by All Ex »

Recently I `ve got a rather crazy idea, I`ve found an extended carton roll and I shaped It, with the proper adaptors to an extension tube. I wonder what 1f, instead of f=200, as my objectives require, make my distance from the sensor, with my tube together (inserting in that number my flange focal distance) 755 mm.
I know that the first problem that I`ll face is the illumination, I`m planning to use 3 flashes in full power. The first thing to do is to measure the magnification with my objectives especially with my recently obtained Mitutoyo 5X 0.14 M Plan Apo.
What do you thi0ng about my experiment?
(For the time being, I`m preparing my rig, If my experiment succeeds I `ll post the results.)
:?:
Last edited by All Ex on Fri Jul 28, 2017 5:51 am, edited 2 times in total.
All--Ex
My YouTube initial video

lonepal
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Joined: Sat Jan 28, 2017 12:26 pm
Location: Turkey

Post by lonepal »

I think you will get a very bad IQ image if you can get :)
You will need a lot of light.

I am very impatient to see the result.
Good luck!
Regards.
Omer

ChrisR
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Location: Near London, UK

Post by ChrisR »

So, are you using a Mitutoyo (infnite) objective without a "tube" lens, and focusing it at 755mm?

Your Objectives should be focused at infinity, not 200mm.
200mm is just the FL of the "tube" lens you need to get the stated magnification.

a 5x mitty is about 40mm FL, so on that extension you'll get magnification about 19x and effective aperture f/333
If my maths is right that's an Airy disc about 0.35mm across. I may be wrong there - it'll be BAD anyway!
But, you never know all that happens until you try, maybe.:)
Chris R

All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

Post by All Ex »

The effective aperture f/333 is something I`ll have to consider very much, in fact, my lighting is not enough.
For starting I intend to place the objective in front of a Nikon Ai 200mm MF focused in the infinity, to see how it compares.
All--Ex
My YouTube initial video

rjlittlefield
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Post by rjlittlefield »

With the rear lens focused at infinity, distance between the objective and the tube lens does not affect magnification or effective f-number.

Greatly extending that distance would serve only to add severe vignetting.

If you add the extension behind the tube lens, then you'll get more magnification and a bigger effective f-number. In that case, the effect of the added extension varies depending on separation between objective and tube lens. Larger separation between objective and tube lens reduces the effect of adding extension behind the tube lens.

--Rik

All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

Post by All Ex »

I`ll work on it, Rik, tomorrow when I`ll have time. It finally seems that I'll need more than I expected.

Thanks for your lights.

:wink:
All--Ex
My YouTube initial video

All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

Post by All Ex »

Eventually, after rearranging my rig to its maximum extension, I`ll have to shorten my carton tube in order to place my Nikon 200mm, as a tube lens
After I` ll test my Mitutoyo 5X I`ll do the same with my Nikon 20X ELWD.
I`ll post the results in that thread.
All--Ex
My YouTube initial video

All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

Post by All Ex »

In the end, my carton "extension tube" broke under its weight.
It has been a long time now that I`m preparing some self-made extension tubes, I hope I`ll post a thread describing my experiences on them (building & results).
All--Ex
My YouTube initial video

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