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")
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[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...
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[Attila]

Many thanks!!!
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[indianadinos]

Thanks for sharing your tips ...
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... and a few other Vivitar, Tamron, Sigma and Soligor lenses ...

[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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