m49 0.5 to 0.75 filter thread adapter ring?

tom_m · Joined: 14 Jan 2018 Posts: 2

I just purchased a Mir 1 silver/white grand prix m39 lens...While waiting on it to be delivered I read that it is an atypical thread pitch? Is this true? m49 x 0.5? I'm getting some conflicting information. The auction said 0.75 but historian sites say 0.5. The logo on the lens is KMZ (but no red P, it is stamped grand prix, so it's not the earlier model).

I'm trying to do as much research as I can, but I'm coming up short. It's rather confusing between the various models (which makes me worry for other reasons as well).

Does anyone know of an adapter or step up ring of the sorts to convert it to something more usable with modern filters?

Thanks!

DConvert · Joined: 12 Jun 2010 Posts: 902 Location: Essex UK

I think you might be adding to the (my) confusion as you mention M39 at one point and M49 at another.
M39 filters are normally 0.5 pitch & M49 are normally 0.75.

I know M42 was used at both 1mm & 0.75mm thread pitches the latter usually called T2 (but some e-bay adapters just call it 'm42' even though this is the usual term for the 1mm pitch)

Some sources claim LTM thread is often described as M39x1mm but is actually M39 at 26tpi (a weird combination of standards)

M39 filter threads are normally M39x0.5 while M49 filters are normally M49x0.75
Most filter threads follow a standard pitch for their diameter though for M37.5 both 0.5 & 0.75 are used.

From the filter listings I've found

size standard pitch
m13.5 x0.5
m19 x0.5
m22.5 x0.5
m25.5 x0.5
m27 x0.75
m28 x0.75
m30 x0.75
m30.5 x0.5
m34 x0.5
m37 x0.75
m37.5 x0.5
m37.5 also x0.75
m38 x0.75
m39 x0.5
m40.5 x0.5
m43 x0.5
m43 x0.75
m46 x0.75
m48 x0.75
m49 x0.75
m52 x0.75
m55 x0.75
m58 x0.75
m62 x0.75
m67 x0.75
m72 x0.75
m77 x0.75
m82 x0.75
m86 x1
m95 x1
m105 x1
m112 x1.5
m122 x1

There are companies like GRB & RAF cameras that will custom make adapters like this if required.

tom_m · Joined: 14 Jan 2018 Posts: 2

Ah I see, sorry about that. I was describing the lens with m39 - mount. From what I read there was a difference in the mir 1 lenses. But I’m getting conflicting info from various places. I guess I won’t really know until I get the lens (though not sure how I could tell the difference other than seeing how a filter goes on maybe), but the last thing I want to do is cross thread or strip something.

I ended up finding raf. I don’t know if I should buy one now, they seem to only have one in stock. They’re $30. Hate to buy something I don’t need of course.

This was one of the sources of confusion. http://camera-wiki.org/wiki/Mir-1 ... the one I got is an earlier model, though I’m unsure if it’s the same as they talk about because so many variants were made or different factories used from what I can tell.

DConvert · Joined: 12 Jun 2010 Posts: 902 Location: Essex UK

jupiter_9 · Joined: 05 Feb 2018 Posts: 6

I have the same problem. I can confirm that some old Russian lenses do come with M49 filter x 0.5. I have Jupiter 9 and Mir-1 which both are in 50s, silver, the 49x0.75 filter cannot fit in them while my silver Helios-44(13 blades) fits perfectly. So I believe that M49x0.5mm filter was created at least in Russian system.