Adjust infinity in Helios 44 M39

[cyberjunkie]

I have repeatedly found on the Internet the (wrong) information about the compatibility of the early M39 version of the Helios 44 with the register of standard M42 (and PK) cameras.
There is about a quarter of millimeter difference. If not adjusted, the lens can be easily fitted on a M42 camera via one of those cheap M39-to-M42 adapter rings, but it would miss infinity by a little.
If the diaphragm is stopped down enough the problem is almost gone, but we don't buy a Helios 44 to stop it down to f/16, isn't it?
Some CLA'ed lenses shipped from Russia or Ukraine are coming with the adapter ring, and already adjusted for spot-on infinity on M42 bodies (or other mounts, using an M42 adapter, as i do with my Pentax DSLR cameras), and this makes the subject even more confusing, because some buyers never encounter this problem and would report in good faith that there is no register mismatch.
This is exactly what happened when i bought a beautiful Helios 40 ("silver", made in 1961 IIRC). It came with the ring and already adjusted, and to my surprise was looking almost new (which suggests a thorough CLA).
The Helios 44 i just received is the aluminium KMZ version with 8 diaphragm blades.
It's in great conditions, and has a non-industrial adapter ring that looks and feels as it has just been removed from the lathe
Unfortunately the infinity is a little off.
I am determined to correct the problem, cause the lens seems to be great, from my first tests.
I would like to avoid to remove some material from the mating surface of the mount, so i would like to know if there is any way to solve the problem in a non-destructive way, for example adjusting the focusing helicoid by the needed amount...
Any suggestion/link/video?
Any feedback would be greatly appreciated.
Thanks

ciao

Paolo

[wolan]

Do a search on this web site, time ago a correct answer was provided to a similar question.

[Lightshow]

The optics unscrew from the helicoid and there are shims between the 2, add or remove as required.

[blotafton]

It can be solved by a m39 adapter and a zenit macro ring. One of the rings in the set has the correct thickness.

Better than working with the lens. For mirrorless cameras only.

[cyberjunkie]

I mentioned the PK mount in my post, but I guess it was not made clear enough...
I need to use the lens on Pentax DSLR cameras, now almost always a K-1 full frame, so I don't need tubes.
It misses infinity by a little, it needs to get closer to the focus plane, not away from it!
As I have already written, the lens came with a M39-to-M42 ring... but the problem isn't caused by the ring (btw, even away from home, I happen to have spares!)
The problem is due to a different register. These early lenses have an M39 thread with a register much longer than Leica rangefinder cameras. Almost identical to M42 Pentax screw-mount... almost!
I found the same kind of problem with Enna lenses that were made with the same mount and a very similar register. Probably they were made for the Braun Paxette, but I'm not 100% sure.
What I know is that they have the same identical problem: with the M39 ring + a PK adapter they miss infinity by a little. Of course it is more evident with longer focals.

ciao, and thanks for the feedback

Paolo

[tomasg]

Paolo, Lightshow showed you waht you have to do....just do that, or if you are skeptical....remove the shim between the optical block and the focusing block...put it back, mount it on the camera and you ll see that now the lens focuses past infinity

[D. P.]

It seems to me that all problems are caused by ignorance.

In the Soviet Union, four variants of M39 threaded mounting were used.

1) M39 - almost complete analog of LTM (L39). For rangefinder cameras. Flange focal distance - 28,8 mm
2) First version of M39 for SLR cameras (until 1967). Flange focal distance - 45,2 mm
3) Second version of M39 for SLR cameras (after 1967). Flange focal distance - 45,5 mm
4) Version for half-frame cameras (18×24 mm). Flange focal distance - 27,5 mm

[cyberjunkie]

[tomasg]

Yes try to hold only the front part of the lens avoiding the two rings. Use some kitchen rubber gloves on the front, they are miraculous sometimes And no hammering whatsoever!

Take a look at my signature for tutorials

Tomas

[Lightshow]

Set the preset ring, the aperture ring and the focus ring to half way positions, this will protect things from bending or breaking.
Grasp the grip around the mount, and grasp the optics section(everything above the focus ring), and turn the optics section in a CCW (counter clockwise) direction to unscrew it. There should be no grub/set screws.

[cyberjunkie]

[Lightshow]

There should be no need to hammer anything in a lens.

[visualopsins]

[Gott23]

[tomasg]

And if one day you want to CLA it click on the link in my signature

[Gott23]

[alex_d]

Im (not) happy to say that if you have just 1 thick alu ring and you remove it,

then aperture ring will be (very possible) blocked.

So its necessary to have a few thin rings to adjust the infinity but also to allow aperture ring to move freely.

[Lightshow]

Ideally you would have a thick ring and a couple thin rings to get the shim thickness correct, but they may have just used a single thick ring that they would sand/file down to the required thickness.

This is my preferred way so you can use the lens on any M42 adapter alongside other M42 lenses.
The other way is to modify an M42 adapter for mirrless cameras, the ones that have a chromed brass insert that's held in by set screws, you can file/sand the rear of the insert to reduce the Registration or add shims to increase it, both will work, but you would have to Cary multiple adapters, one dedicated to the lens.

To make the shims from shim stock wouldn't be simple onless you have access to a lathe, then you can make 2 sets of dies to clamp the shim stock and turn away the excess.
Without access to a lathe, you can still make the shims relatively easy, you'll need 2 round bars with the correct diameter (or one with 2 diameters on each end, and clamp the shim stock to the end of the rod against a flat surface, use a sharp razor blade or other tool that is sharp and scratch around the circumference till you break through, then smooth off the edges with sandpaper so they won't cut you. So you would reduce the thickness of a thick shim and then add thin shims to fine tune the thickness.

Of course all this depends on if you can't reach infinity(shim is too thick) or focus past infinity(shim is too thin).

[alex_d]

well, calculated and i need to shim 0.9mm max from this 1 think alu ring.

Have already flattening thick glass with fine sandpaper so it shouldn't be a problem.

well a bit of a mess ...

[Lightshow]

Yes, sanding down aluminum is a bit messy, your hands get stained, latex/nitrile gloves help, so can soapy water.

[alex_d]

well, been sanding down the head of one of my two strokers recently - imagine the mess,

this tiny ring is a piece of the cake,

but still have to do it in the kitchen, so ..