Need help with MIR-24N (M42 converted) lens to fit it to the JTAT adapter

Hi

I have this MIR-24N lense which was converted to M42 before I bought it.





It is a Nikon mount lens (as fas as I know) converted to M42. The problem is the protruding parts seen as labled 1, 2 and 3 in the below picture. I removed the lever marked 1 as this caused the aperture to stuck as the lever could not move when the adapter was screwed on. Now the adapter can be screwed further in and now it just hits the protruding parts of the aperture ring labeled 2 and 3. The diameter of the JTAT is just too big by 1-2 mm or the lense is too small. What should I do? Grind down the aperture ring? I have seen others use this lens on SD cameras but maybe that was SD10 or SD9...





Hints much appreciated!

Interesting, is your lens M42 plate placed at correct registration distance (45.46mm) or at Nikon distance (46.5mm)? If the later, then you could install some shims between M42 plate and lens. Otherwise you probably have to grind protruding parts down (if you cannot remove part of aperture ring).

I've got M42 variation of same lens (Mir-24M). Do you need some distance measures from there? Unfortunately mount part (including aperture ring) looks quite different.

--
Arvo
Sigma/Foveon information collection and little gallery:
http://www.stv.ee/~donq/sigma.htm
http://www.stv.ee/~donq/images.htm

Not sure. The rear plate of the M42 is level with the edge of the lens. The protruding parts is about 1mm. So should the rear plate then be at the level of the protruding parts. I'm not 100% sure how this plays out with the registry distance.

Comparing this lens to my Nikon 50mm AF-D (I also have a Nikon DSLR) the M42 plate seems to be at the same level as the F-mount plate. So that means I should add some 1mm shims below the M42 rear mount?

See the image of the 50mm AF-D:



Same protruding parts. Back-plate at same level as the M42 I have.

Do you have the MIR-24N (or 24H as it is written in Russian) or the MIR-24 ?

PrebenR said:

Comparing this lens to my Nikon 50mm AF-D (I also have a Nikon DSLR) the M42 plate seems to be at the same level as the F-mount plate. So that means I should add some 1mm shims below the M42 rear mount?

See the image of the 50mm AF-D: http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/AFNikkor/images/NikkorlensADDrear.jpg

Same protruding parts. Back-plate at same level as the M42 I have.

Click to expand...

I would add 1mm shims (or even some temporary spacers) and check for infinity focus.

PrebenR said:

Do you have the MIR-24N (or 24H as it is written in Russian) or the MIR-24 ?

Click to expand...

Mir-24M. I think M means M42 (N would mean Nikon).
http://www.ussrphoto.com/wiki/default.asp?WikiCatID=84&ParentID=4&ContentID=691

--
Arvo
Sigma/Foveon information collection and little gallery:
http://www.stv.ee/~donq/sigma.htm
http://www.stv.ee/~donq/images.htm

PrebenR said:

Hi

I have this MIR-24N lense which was converted to M42 before I bought it.





It is a Nikon mount lens (as fas as I know) converted to M42. The problem is the protruding parts seen as labled 1, 2 and 3 in the below picture. I removed the lever marked 1 as this caused the aperture to stuck as the lever could not move when the adapter was screwed on. Now the adapter can be screwed further in and now it just hits the protruding parts of the aperture ring labeled 2 and 3. The diameter of the JTAT is just too big by 1-2 mm or the lense is too small.

Click to expand...

Sounds like it might have been converted to M39 instead of M42?...Measure across the thread and if its 39mm in diameter you will need an M39-M42 thread adapter:

http://www.ebay.co.uk/itm/M39-Lens-M42-mount-39mm-42mm-camera-adapter-Ring-/180805533015?pt=UK_Photography_CameraLenses_Lens_caps_hoods_adaptors_ET&hash=item2a18d97d57

DaSigmaGuy said:

Sounds like it might have been converted to M39 instead of M42?...Measure across the thread and if its 39mm in diameter you will need an M39-M42 thread adapter:

http://www.ebay.co.uk/itm/M39-Lens-M42-mount-39mm-42mm-camera-adapter-Ring-/180805533015?pt=UK_Photography_CameraLenses_Lens_caps_hoods_adaptors_ET&hash=item2a18d97d57

Click to expand...

It measures 42mm across. And the adapter screws on smoothly. Only that it will just hit the protruding parts. It semms as if it could go down some 0.2 mm more it will hit the bottom as the inside ring of the back plate is slightly elevated. You can see that on the picture in the previous posts. The screws are placed just on the edge.

But what I'm wondering is if the registry distance of the Nikon is 46.5mm and SA is 45.46mm then I need the lens 1 mm further away from the sensor, right?

How can I test if it is at correct registry distance? Will it be visible as front/back focusing in the photos?

I have been trying to google, but I only find adapters for M42 for Nikon camera, and not the other way.

PrebenR said:

But what I'm wondering is if the registry distance of the Nikon is 46.5mm and SA is 45.46mm then I need the lens 1 mm further away from the sensor, right?

How can I test if it is at correct registry distance? Will it be visible as front/back focusing in the photos?

Click to expand...

Just check infinity focus.

If registration distance is correct, then infinity focus is exactly at the end of focus scale. (For MF lens there is no point extend focus scale above infinity; for AF lens it is usually a bit extended.)

If lens is too near (reg distance below normal), then you are able focus past the infinity.

If lens is to far (reg distance to big), then you cannot focus to infinity at all.

--
Arvo
Sigma/Foveon information collection and little gallery:
http://www.stv.ee/~donq/sigma.htm
http://www.stv.ee/~donq/images.htm

PrebenR said:

DaSigmaGuy said:

Sounds like it might have been converted to M39 instead of M42?...Measure across the thread and if its 39mm in diameter you will need an M39-M42 thread adapter:

http://www.ebay.co.uk/itm/M39-Lens-M42-mount-39mm-42mm-camera-adapter-Ring-/180805533015?pt=UK_Photography_CameraLenses_Lens_caps_hoods_adaptors_ET&hash=item2a18d97d57

Click to expand...

It measures 42mm across. And the adapter screws on smoothly. Only that it will just hit the protruding parts. It semms as if it could go down some 0.2 mm more it will hit the bottom as the inside ring of the back plate is slightly elevated. You can see that on the picture in the previous posts. The screws are placed just on the edge.

But what I'm wondering is if the registry distance of the Nikon is 46.5mm and SA is 45.46mm then I need the lens 1 mm further away from the sensor, right?

Click to expand...

Actually the registration distance of the SA mount is 44mm...The 2.5mm difference is what makes the new Nikon adapter possible.

DaSigmaGuy said:

PrebenR said:

But what I'm wondering is if the registry distance of the Nikon is 46.5mm and SA is 45.46mm then I need the lens 1 mm further away from the sensor, right?

Click to expand...

Actually the registration distance of the SA mount is 44mm...The 2.5mm difference is what makes the new Nikon adapter possible.

Click to expand...

Yes, but this lens has been converted (not by me) to M42 and I'm using the M42 adapter. Does this not work then?

ArvoJ said:

Just check infinity focus.

If registration distance is correct, then infinity focus is exactly at the end of focus scale. (For MF lens there is no point extend focus scale above infinity; for AF lens it is usually a bit extended.)

If lens is too near (reg distance below normal), then you are able focus past the infinity.

If lens is to far (reg distance to big), then you cannot focus to infinity at all.

Click to expand...

Thanks for the explanation. I added some cardboard paper to increase the distance so the protruding parts just went clear of the adapter. Now when I tried to focus to infinity it doesn't seem it manages. I think I have to grind down the protruding parts to manage to get the lens to work properly.

Here is a test shot. I focused on the trees and not the goat...

It doesn't matter, where you focus visually - registration distance doesn't change mirror alignment, it just changes focusing distance limits. Systematic back- or front focus for manual focusing means that you have your mirror misaligned, this is not lens dependent.

Just turn lens focus scale to infinity end and take some images - where's focus on these images? (If that is what you did then sorry about my misunderstanding).

But yes, if you can't reach infinity focus this way, then grinding down these parts would be only good choice.

Well, you could relax focus ring screws and adjust focus limiter - this can work, but no one knows, how much room there is for such adjustments left. I've not disassembled this lens, for some other old lens there was prcatically no room left for adjustment.

--
Arvo
Sigma/Foveon information collection and little gallery:
http://www.stv.ee/~donq/sigma.htm
http://www.stv.ee/~donq/images.htm

ArvoJ said:

Just turn lens focus scale to infinity end and take some images - where's focus on these images? (If that is what you did then sorry about my misunderstanding).

Click to expand...

Yes, I did that

ArvoJ said:

But yes, if you can't reach infinity focus this way, then grinding down these parts would be only good choice.

Well, you could relax focus ring screws and adjust focus limiter - this can work, but no one knows, how much room there is for such adjustments left. I've not disassembled this lens, for some other old lens there was prcatically no room left for adjustment.

Click to expand...

Some more testing and it seems like I have to adjust the lens further away. What I did was to turn the lens a bit loose (after removing the cardboard paper). It seems that if I turn the lens almost 1/2 turn counter clockwise (loosening the lens from the adaptor a bit) then I get infinity in focus. If I don't do this then I don't get focus on infinity.

So I'm testing this and will try to put the thinner card board paper in stead. But it is getting dark outside so I have to continue testing tomorrow. :-(

PrebenR said:

Some more testing and it seems like I have to adjust the lens further away.

Click to expand...

Hmm, this means that your lens focused past infinity. This would be no big problem - at least you can get infinity focus by turning focus ring a bit (to 5m or 10m mark or so); of course this is not convenient.

Tele lens are much simpler to adjust 35mm has even at full aperture enough big hyperfocal range, from about twenty meters to infinity or so.

--
Arvo
Sigma/Foveon information collection and little gallery:
http://www.stv.ee/~donq/sigma.htm
http://www.stv.ee/~donq/images.htm

PrebenR said:

DaSigmaGuy said:

PrebenR said:

But what I'm wondering is if the registry distance of the Nikon is 46.5mm and SA is 45.46mm then I need the lens 1 mm further away from the sensor, right?

Click to expand...

Actually the registration distance of the SA mount is 44mm...The 2.5mm difference is what makes the new Nikon adapter possible.

Click to expand...

Yes, but this lens has been converted (not by me) to M42 and I'm using the M42 adapter. Does this not work then?

Click to expand...

It looks like the rear element prodrudes quite a bit past the M42 plate at infinity so you should be able to use a shim to bring the M42 mounting plate away from the protruding parts on the rear of the lens allowing the M42 adapter to screw on further and the lens will still reach infinity focus.

The only thing you might have to worry about is the length of the securing screws...If they are short you might only be able to use a thin shim, say up to 0.5mm thick, but if they are long enough you should be able to use a shim of at least 1mm thickness or more.