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Long focusing helicoid for small lenses

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#1 UlfW

    Ulf W

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Posted 26 August 2017 - 15:03

I wanted to extend the focusing range for my El-Nikkor 80 and 105mm lenses.
I reached infinity with my first combination of extension rings and a 24-55mm M42 focusing helicoid, but wanted to be able to get more close in the macro end.

The solution was to get a bigger 35-90mm long helicoid with M52 threads in one end.
This helicoid has an opening that is wide enough to allow the lenses inside.
I glued a short m42 extension tube in the bottom of the front part of the helicoid and selected another tube for the lens to make it possible to access the aperture ring on the lens.

Attached Image: IMG_1367.JPG
The tube I glued was filed shorter, ca 1mm in the male thread end, to go as deep as possible without reaching the rear structure.

Attached Image: IMG_1369.JPG
In the shortest position I can still focus at infinity and reach the aperture ring.

Attached Image: IMG_1370.JPG
The M52 helicoid has a longer total turning range during adjustment (1-3/4 turn)
and seems to give the same focusing resolution as the old M42 helicoid.

The parts were bought at eBay:
http://www.ebay.com/...e-/282303765481
http://www.ebay.com/...g-/220946248717
Ulf Wilhelmson
Curious and trying to see the invisible.

#2 Andrea B.

    Desert Dancer

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Posted 26 August 2017 - 15:05

That is a really nice adaptation!

Thanks for sharing this with UVP.
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 enricosavazzi

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Posted 26 August 2017 - 20:08

Reminds me of a similar adaptation I did a few years ago for the 60 mm UV Rodagon, see third picture from the top of the page at:
http://savazzi.net/p...ng_helicoid.htm

PS - if anyone has my book "Digital photography for science", Fig. 6.5.E shows some details of the modification.

Interesting that the 52 mm focusing helicoids now have a longer focusing rotation. When I bought mine some 5-7 years ago, they did not.

Edited by enricosavazzi, 27 August 2017 - 07:29.

-- Enrico Savazzi