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I-50 RF to closer focus
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PostPosted: Tue Apr 13, 2021 8:30 am    Post subject: I-50 RF to closer focus Reply with quote
Hi,

is it possible with not to much butchering to bring the focus closer than 1m,

42mm sibling has 0.65m what is not great but still better than rf/39mm version

Cheers


PostPosted: Tue Apr 13, 2021 10:14 am    Post subject: Reply with quote
You could always go for extension rings in either the camera or lens mount.


PostPosted: Tue Apr 13, 2021 4:47 pm    Post subject: Reply with quote
Depending on the camera you are using there may be an adapter available with built-in macro focusing helicoid. Definitely avalable for Leica M to Sony E-mount. M39 RF lenses are easily adaptable to Leica M.
I preferred to use these adapters with my RF lenses before I bought the Techart PRO AF adapter which provides similar functionality.


PostPosted: Tue Apr 13, 2021 10:01 pm    Post subject: Reply with quote
The helicoid isn't really designed to extend that far, so you would require something else to help it gain that extra distance from the sensor, that leaves you with tubes, or a helicoid adapter.

A different path is to look for an m39 Macro lens, there are some out there.
https://www.ebay.com/itm/EXC-the-Rarest-Russian-lens-FED-MACRO-3-5-50-RANGEFINDER-camera-Zorki-Leica-M39/402177567700
Not the cheapest option in this case.
The optics are the same, but the helicoid was designed with extra extension distance, that's why it is physically longer than a typical LTM 50.
Hmm, looking at this lens and comparing it to this lens: https://www.ebay.com/itm/EXC-FED-36-f-6-3-100mm-Rangefinder-Lens-M39-LTM-MADE-IN-USSR/113943518772
I wonder if they just swapped optics, does the above 50mm Macro focus to infinity? I've never seen one in person so I'm not sure.


If you're really ambitious, you could transplant the optics into a longer helicoid, you'd need access to a metal lathe to modify the parts and make the helicoid.


PostPosted: Wed Apr 14, 2021 12:21 am    Post subject: Reply with quote
Well, the OP is talking about a reduction of the minimum focus distance (MFD). The adapter I've mentioned reduces the MFD from 1 m to apprx. 42 cm whilst still enabling infinity.
It's not a "macro" but a close focus adapter. I should have stated it more precisely.


PostPosted: Wed Apr 14, 2021 9:27 am    Post subject: Reply with quote
Hello,
Thanx for reply's.

At infinity, measuring both lenses side by side with removed RF tube,
i see the external measures the same - even the focus helicoid is the same length.

At the minimum focus distance, 42mm screws 7mm more out of the outer lens housing.

Seeing this, it gave me the idea that lenses are very much the same construction (well surprise!) but that 39mm has an early 'stop' to prevent focusing less than 1m.

So reported shorter helicoid on 39mm does not fit my measurements.

Has anyone compared both dismantled lenses side by side ?


Further,
The lens is used with M39 > FX adapter for normal daily shooting and not for any macro work.
It fits perfectly in a light minimal set of other 39mm lenses.
Any helicoid adapter that I found on-line is too bulky as they are minimum/only 42mm.
There is L-mount helicoid adapter but this setup is getting expensive and complicated ...
So I prefer to stay on the thema about modifying the lens instead of work-around adapters

Cheers


PostPosted: Wed Apr 14, 2021 11:16 am    Post subject: Reply with quote
well, im happy to report that I fixed the minimal close focus by removing 1 stop-screw,

took both 39 & 42 apart,

now 39/rf model focus down to appx .45-.5m with the original rf tube.


its also very rewarding to put back this T-43 grease back on the helicoid to improve focusing resistance.


I would not suggest this mod to use it on rangefinder film camera.

Cheers


PostPosted: Wed Apr 14, 2021 9:52 pm    Post subject: Reply with quote
Nice to know you got it to focus closer, congratulations, hope you can post some pics showing what you did to assist others heading down this path.


PostPosted: Thu Apr 15, 2021 11:08 pm    Post subject: Reply with quote
If we are talking LTM you can couple a LTM to Leica M adapting ring with a Leica M to Sony E macro focusing helicoid adapter. Thar should get you to about 20cm. Unscrewing the lens partway gets you closer. I don't know if such adapters exist for other mirrorless mounts.


PostPosted: Fri Apr 16, 2021 8:29 am    Post subject: Reply with quote
kymarto wrote:
If we are talking LTM you can couple a LTM to Leica M adapting ring with a Leica M to Sony E macro focusing helicoid adapter. Thar should get you to about 20cm. Unscrewing the lens partway gets you closer. I don't know if such adapters exist for other mirrorless mounts.


You could always use a short M42 adapter (a couple mm long), add 42mm (or even better 52mm with step up and down rings) focusing helicoid of a suitable length, combine it with an extension tube to get the best possible flange distance and there you go. Depending on the helicoid you could get really close. It could be a more flexible solution.


PostPosted: Fri Apr 16, 2021 8:47 am    Post subject: Reply with quote
Dejan wrote:
kymarto wrote:
If we are talking LTM you can couple a LTM to Leica M adapting ring with a Leica M to Sony E macro focusing helicoid adapter. Thar should get you to about 20cm. Unscrewing the lens partway gets you closer. I don't know if such adapters exist for other mirrorless mounts.


You could always use a short M42 adapter (a couple mm long), add 42mm (or even better 52mm with step up and down rings) focusing helicoid of a suitable length, combine it with an extension tube to get the best possible flange distance and there you go. Depending on the helicoid you could get really close. It could be a more flexible solution.


You can buy a 10-15.5mm helicoid, but you will not be able to focus to infinity because the adapter ring adds 1mm. The extra distance needs to be 10.8mm for infinity and you end up with 11mm. The Leica M to Sony E adapter I have extends to 15.5 mm, just like the 10-15.5mm helicoid, but the adapter is built in so you get infinity and the same close focus distance. A short M42 helicoid with a M39 adapter ring works well if you don't need infinity, because at 15.5mm you can get close, but sometimes not close enough, and adding the shortest existing extension tube @ 10mm puts you often too close.


PostPosted: Fri Apr 16, 2021 12:17 pm    Post subject: Reply with quote
Quote:
Nice to know you got it to focus closer, congratulations, hope you can post some pics showing what you did to assist others heading down this path.



I have made no pictures but Ill explain it as is very simple and straightforward.

Tools: a good sharp 1mm wide screw driver, pointy pliers, tweezers.

Tiny lens screws: unscrew them max 1/2 of the turn (appx -180* degree) CCW.

1. Remove RF tube (first make the screw lose a bit),
2. remove RF focus-pushing tube - unscrew it CW,
3. turn focus to infinity,
4. on the focusing barrel make 3 screws lose, note (or make pics for yourself..) that your barrel is at Infinity all the time,
5. take of the focusing barrel off, notice pointy marks that tiny screws have made .. you have to place them back in the same tiny holes (marks),
6. while focus is still at Infinity, turn the focusing barrel to closest focus and note the stop screw - this one has to go out,
7. with a pointy pliers unscrew it, may use tweezers when this screw becomes lose. Remove that screw from the lens and save it.
8. Note the T-43 grease that fell of the helicoid - put/smear it back and turn the focus few times and check how that grease spread on the helicoid thread. Clean where needed, also under the lens too.
9. Turn focus to the closest and inspect if both screw-heads are stopping each other, if yes - its done, put everything back on the lens.
If not (what I had on M42), then one of the remaining screws is hair too short - you need a bit longer screw or a very very tiny washer under.
10. In reverse order 5 > 4 > 3 ...
11. test

thats all
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