Adjust Infinity Focus - Mir-24N 35mm f2.0

[caerwall]

Bought a Mir-24H which was in good order but would not focus beyond 2/3 metres.

Did not know how to adjust infinity focus and in fact it was so far out that I thought the helical tracks were not lined up properly.

No manuals or instructions on the web so I thought I had better teach myself.

The way into the lens is via the front plate. Screw out the faceplate with a rubber tool or something grippy that will not damage the front lens element. Take care - this holds the first front lens element in place in this particular lens and it will fall out once the cover is removed.

Underneath are three screws one of them having a location scratch conveniently left for me to show alignment. But before you go any further it is best to take off the back plate as well to help reassemble the lens afterwards. Underneath is a house of horrors and I am glad that I did not need to go any further in that direction.

Back to the front of the lens. I put a piece of masking tape across the focus ring to focusing scale and carefully cut it so that the focus ring could move. This was to allow subsequent re-alignment but in fact I did not really need it but it helps to be safe rather than sorry. If you only need to make a small infinity focus adjustment you can skip all the palaver and just do the following which is probably necessary also as a last item after a more detailed pull down and lubrication.

I will get the final infinity focus adjustment out of the way:

First visually find infinity focus - I am talking digital cameras here and it is easy to do - if the adjustment is out then the scale is wrong and wherever your eyes tell you is right is when infinity is. My original problem was too close so the focus ring was not ever going to find infinity - I would have to loosen, adjust tighten, etc until the camera found infinity focus somewhere. Then I might get it right.

Around the grip are three tiny screws I found that if I backed these out right until they were about parallel to the grip surface they did not fall out and the focus ring was loose enough to turn without turning the lens body underneath. If the lens was on infinity focus then it is simply necessary to turn the indicator to the infinity mark and re-tighten the focus ring. Job done. Note: that if you think there is any danger of the screws falling right out it is best that you remove them completely as they are so small as to be easily lost - better have the fiddle of getting them back in than losing any. I took a chance and the screws stayed put.

However I was not up to this at the time and I thought that the helical settings were out - maybe they were not but just as soon as you remove the three screws at the front of the lens the front component wants to come out - there is a pin-lever at the very end that fits in a slot in the aperture mechanism and as you have taken the back of the lens off you will of course wish to observe were this pin fits as it comes out as it is harder to figure out afterwards as I had to do. The front component fits in rails and is not over complicated to remove or replace except that it will not go back properly until you get that aperture operating pin right.

If your helicals are wrongly set or you need to re-lubricate then screw the helicals out. Otherwise best left alone - I had a few happy hours and about 16 attempts to get the combination right. There are internal and outer helical tracks and a free double sided one in-between. You will have had to back out the focus ring screws to get the ring off and separate the helical rings. If you are in there for lubricating purposes - do it now.

Getting the right setting for the helix is hard - I found out by trial and error - it seems that the free ring should be screwed almost in first and then the front ring screwed in so that the front of the lens left about a gap of 2mm with the lens setting at infinity. Not sure exactly what worked in the end it just did and I was happy but if someone can establish a scientific method we will all be happy.

Putting it back together is fairly straight forward - if you know where the aperture operation pin goes - easy. If you have marked one of the three screws at the front easier still. Once one screw goes in test the focus movement - if it is completely locked up - try again. If the focus is "nearly right" then it can be adjusted. If it seriously binds at infinity then you need to try again as well.

Presuming that you are either naturally gifted, or have done this before the lens will be within a reasonable range of being right and you can replace the other two screws. Otherwise summon some reserves of patience and have another go at getting the helicals right. Repeat until you have it right - hopefully you have not become mad.

Once the lens is back together I found my "infinity" was 15 metres. Loosen the grip screws as above and so very carefully inch the detached focus ring around without moving your carefully set helical underneath until the infinity mark is correctly placed. Once I did this the lens focuses perfectly.

Another one down.

Tom

[Orio]

hi, I corrected the thread name, because the correct name of the lens is MIR-24N
(where the N stands for "Nikkor")

[caerwall]

Thanks Orio

I am aware that the Latin "N" translates to the Cyrillic "H" and vice versa. This lens is a "Latin script" Mir-24N but in one of the crazy quirks of the Russian lens naming system is no "Nikkor" but very much a M42 mount.


Mir-24N or Mir-24H it is the same lens.

Tom

[LucisPictor]

Thanks for the description. Might come in useful one day...

[Attila]

Many thanks!!!

[indianadinos]

Thanks for sharing your tips ...

[Orio]

[caerwall]

Orio,

It is certainly an oddity, this lens has the Zavod Arsenal logo on it and distinctly 24H (cyrillic) and it is M42 mount. I agree that if you check ebay listings the Mir-24N is almost always Nikon mount.

There is another Mir-24N (cyrillic H) M42 mount currently listed on ebay and it looks exactly like the one I own. (Mine is 1987 build)

http://www.ebay.com.au/itm/MC-Mir-24-2-35mm-lens-M42-Zenit-Pentax-Praktica-V-GOOD-/390326510187?pt=Camera_Lenses&hash=item5ae145e26b#ht_1204wt_1137

Perhaps the Zavod Arsenal retro-fitted some M42 mounts on the Nikon mount production but did not change the front plates?

One of life's curiosities - does it make mine "valuable"? (grin).

Tom

[caerwall]

Some images - sorry I did not take any with the helical drives removed

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[yattiaman]

Hello guys,

sorry to resume such an old post, but I just registered to the forum because I have a big problem. The positive side is that I found this interesting forum on manual lenses, will be useful in the future.
I have a mir 24N just bought from ebay, it was pristine, in smooth working condition and aesthetically perfect.
It only had a problem: a big particle of dust inside, I didn't realize it was near the front group.
So first mistake, I opened the lens from the back. Second mistake: it looked so logical at the time, that I didn't take a picture of the location of the components. I cleaned the first 3 lenses and tried to reassemble it.
Needless to say it's a pain in the ankle...A big issue even finding the right combination to screw back the barrel group onto the external case. Now, I am not sure I did it right, but this is not the worst part: I have no idea how to reattach the spring, it really looked such a smart mechanism at the beginning, that I thought it would be very simple to put it back. Now, I extended the spring a few times in the wrong direction and it's bent, longer and almost broken.
That's why I need your help: could some of you who own a similar lens do me the favour to open the alu back plate and take and post a picture to show the right position of its parts? I have trouble even with the diaphragm black metal connector, the long flat part which protrudes from the back of the lens to actuate the diaphragm. It should fit in the related slot on the alu backplate once assembled, but it's in the opposite position, sounds weird, but if I screw it back on the barrel it seems it's in the right place on the barrel but it doesn't match the opening on the back plate.
And the other part I am not sure about is the L shape grey metal stopper. I don't remember where it goes. I put back the guides and the aperture pin, but I really forgot how to reassemble the aperture mechanism, I only need a few steps to finish, but I have been stuck for days. And I'd like to avoid buying a new one...
I really hope some of you can help me. I don't need you to disassemble the lens, but just open the back and show me where each part goes...There are no photos on google, I have been searching for 2 days...
THANKS IN ADVANCE!

[xslavic]

I myself had problems realigning this lens ,so i uploaded this picture to help.

[Lloydy]

[MMouse]

Interested into this topic...

[Jonk]

caerwall is right about the optics wanting to come out once the name ring is unscrewed. I wanted to sort the aperture out on my lens last night and went into to lens from the front using caerwall's instructions. As advised the front element was loose once the name ring was removed. I removed it with a plunger and placed it on a pec pad.

What I didn't realise is the optics below also aren't held in by a retaining ring. They look like they are secure because there is a retaining ring at the front, but that is only holding them inside a silver assembly that is loose in the lens. This is just a word of warning as they unexpectedly came out while I was working on the lens. Luckily the optical block fell into my hand and I quickly placed it back in the lens without any damage or contamination. I once had an optic from another lens get a nasty chip when it fell out unexpectedly and landed on my spanning wrench. That was a cheap lens with fungus thankfully.

I opened the lens to sort out the aperture which wouldn’t open fully. I wasn’t losing much light but it was still annoying. I realised I could fix it when I saw the construction of the inner barrel in caerwall’s photos. You can adjust the aperture range by loosening the screws holding either of the silver strips next to the aperture lever on the inner barrel. You then move the strip to the side so the aperture lever can move further. I loosened the screws and adjusted the wrong strip at first which in hindsight was good because my lens didn’t use to stop down to f22. I sorted out the other side and now the lens opens fully. I would only recommend moving the strip as much as needed as we have no idea what happens if the aperture lever moves too far.

#1

I’ve labelled the screws on one of caerwall’s images. I hope it’s ok to use the image. I would have taken my own but my hands were shaking from anxiety when working on the lens. I just wanted to get the job done without causing any damage. I’m used to working on cheap spares repairs lenses. This is the most nerve-wracking repair I’ve done. I re-lubed a Jupiter 3 using Retro Foto House’s YouTube video a while ago and that was less nerve-racking.



This is my lens before the repair.

#2