Meyer Telemegor Mystery - Help!

[David Murphy]

This is my pretty Telemegor 400mm F5.5, recently purchased from a seller on the Bay with a nice original box. I thought this lens was for Exakta, but in testing it I find it has a bayonet mount that's not Exakta. I know it's not for Praktina either (I own one). The inner dimension of the exit point of the lens is about 36mm in diameter probably indicating a 35mm lens (ruling out Praktisix).

Does anyone here know what camera this lens was designed for?

 

[xayraa33]

could it be for a Robot Royal camera David?

 

[bcostin]

Could it be the less common Exakta outer-bayonet mount? Unfortunately I don't have a lens that uses the external flanges for comparison.

I have that same Telemegor lens in M42 mount. It's heavy, but pretty nice for an older telephoto. And it certainly looks very impressive. 🙂

 

[David Murphy]

Yes I think you are correct. After some digging with Google, I'm coming to the conclusion that this is the so-called Exakta "outer bayonet" mount. Apparently this outer bayonet mount was introduced with the second version of the Exakta VX. The idea is similar to the idea behind the Contax RF, Nikon RF, and Canon 7 external bayonet mounts -- it's designed to give more rigidity and strength to the mating between a camera body and heavier lenses. Unfortunately my Exakta body is version 1 of the VX, which has only an internal bayonet -- thus my confusion.

 

[David Murphy]

Yes, the lens is a real beauty by the way - clean as a whistle and built like a tank. I was planning to use this for astrophotography with its light gulping 73mm effective aperture. I may keep it till I can find a working Exakta with an external bayonet mount (good working Exakta bodies are hard to find though)

 

[varjag]

More likely though is is Pentacon Six mount.

http://www.pentaconsix.com/P6data.htm

 

[Roger Hicks]

My immediate thought was Pentacon 6 too but I happened to have one beside the computer and it doesn't look the same: the Pentacon 6 mount has a locating pin in the middle of the upper bayonet lug, not to one side like this.

Cheers,

Roger

 

[Mark Wood]

From the pictures, I wonder if the bayonet ring could be non-original? Could this have been adapted for a Kiev 88 (or Salyut)?

 

[David Murphy]

The reason it's not Pentacon 6 (or related format mount) is that the diameter of the exit stop is too small -- about 36mm. Remember Pentacon (or Praktisix) is a 60mm X 60mm frame, so the diameter of the light path at the back of the lens would have to be in the neighborhood of perhaps 65-70mm or so, or else serious vignetting would occur. This further argues for external Exakta bayonet mount.

 

[Mark Wood]

Apologies, I hadn't thought properly about the dimensions. The locking pin and the bayonet lugs look to be in the right positions for Exacta.

 

[varjag]

Haven't thought about dimensions, right.

 

[rxmd]

The reason it's not Pentacon 6 (or related format mount) is that the diameter of the exit stop is too small -- about 36mm. Remember Pentacon (or Praktisix) is a 60mm X 60mm frame, so the diameter of the light path at the back of the lens would have to be in the neighborhood of perhaps 65-70mm or so, or else serious vignetting would occur.

That in itself is not a reason.

The rear element of the Flektogon 50/f4 in Pentacon Six mount has a diameter of less than 2 cm. On the 180/f2.8 Sonnar it's difficult to measure, but I would presume it's less than 4 cm as well.

Philipp

 

[David Murphy]

That in itself is not a reason.

The rear element of the Flektogon 50/f4 in Pentacon Six mount has a diameter of less than 2 cm. On the 180/f2.8 Sonnar it's difficult to measure, but I would presume it's less than 4 cm as well.

Philipp

Yes, but this essentially a field stop, not a rear element. Rays from a rear element can diverge far off the optical axis in a non-telecentric fashion to illuminate a 6X6 field. This is a field stop (or close to it) and the nearest lenses are far upstream inside the lens. Anyway viewing images of the Exakta outside bayonet mount on the Web, it seems that the geometry is right for mating this lens to it -- it is easy to get fooled though with lens mounts.