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No name 50mm/2.8
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PostPosted: Sun Jun 27, 2021 2:25 pm    Post subject: No name 50mm/2.8 Reply with quote
I tested a lens I have recently received.
It's a rather small lens, (front lens is between 1cm et 1.5cm wide). It has an Helios like design. I tested it, it has ~50mm focal lenght, and max relative aperture ~f2.8. It covers 24x36 without problem is give relatively good results on the whole plane at infinity, so it was made for 24x36. It had a diaphragm, but it was removed. The body shows that it had a focus system, and that the lens was mounted on the nose on some machine. Results definitly exclude the IR lens hypothesis. So I believe something technical, but I don't know which one. Reproduction machine rarely use helios design. Might be for a surveillance camera, but the body material looks old, more from the 50-60's than 70-80's.

Anyway, I like the results it gives on my A7.



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Best regards,


PostPosted: Sun Jun 27, 2021 2:43 pm    Post subject: Reply with quote
Sweet mystery lens. I like the bokeh. Like 1

Could it be a Heligon or Xenon?


PostPosted: Sun Jun 27, 2021 7:03 pm    Post subject: Reply with quote
blotafton wrote:
Sweet mystery lens. I like the bokeh. Like 1

Could it be a Heligon or Xenon?


I don't think so, I found this lens on ukranian market, I believe it's a soviet lens.


PostPosted: Sun Jun 27, 2021 8:57 pm    Post subject: Reply with quote
Nice results. Balance between focus sharpness and OOF character makes it looking close to a projection triplet.


PostPosted: Sun Jun 27, 2021 11:34 pm    Post subject: Reply with quote
Looks like a nice chunk of brass, which IMO excludes a soviet lens which would likely be aluminum, not brass.
The results are very nice, well worth the effort to clean up properly, and even have it transplanted into a helicoid/body.

You didn't mention it's back focus, that will help narrow down the search, measure from the film plane to the rear element(smaller element), and again measure from the film plane to the centre of the aperture slot.
While it's getting cleaned, try to create a drawing of the shapes of it's lens elements, this will expose its family heritage, which will aid in deducing its manufacturer and ultimately what lens it is.
Should be a fun little puzzle to solve and use.


PostPosted: Sun Jun 27, 2021 11:41 pm    Post subject: Reply with quote
Reminds me of the Domiplan. A triplet?


PostPosted: Mon Jun 28, 2021 9:20 am    Post subject: Reply with quote
hi,
looks like the inner part (lens section) of a usual lens with removed aperture blades.


PostPosted: Mon Jun 28, 2021 5:54 pm    Post subject: Reply with quote
Lightshow wrote:
Looks like a nice chunk of brass, which IMO excludes a soviet lens which would likely be aluminum, not brass.
The results are very nice, well worth the effort to clean up properly, and even have it transplanted into a helicoid/body.

You didn't mention it's back focus, that will help narrow down the search, measure from the film plane to the rear element(smaller element), and again measure from the film plane to the centre of the aperture slot.
While it's getting cleaned, try to create a drawing of the shapes of it's lens elements, this will expose its family heritage, which will aid in deducing its manufacturer and ultimately what lens it is.
Should be a fun little puzzle to solve and use.


Soviets also used brass. See for exemple this OF-184 (1955)

Same for Industar-4 and other technical lenses.

I did not measured the back focus distance precisely, but distance at infinity looks like it could be used for M42 mount lens. Here is the lens set at infinity on the A7.



As considering the optical design, the rear group is really easy to remove (just unscrew). The intern side is like on helios design, and the reflexion let me guess it has 2 separated elements. The rear element looks the same, but a bit bigger. That's why to me, it definitly looks like a double gauss planar type, so Helios if it has soviet roots.

Here is the rear group.
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PostPosted: Mon Jun 28, 2021 5:57 pm    Post subject: Reply with quote
planet.groove wrote:
hi,
looks like the inner part (lens section) of a usual lens with removed aperture blades.


Usualy, the lens block is separated from the focus block.
Here, this part also has focus helicoidale part, which is not usual. That's why I think it was mounted directly on a technical thing, the body inside the machine, screwed by the nose, and only letting see the frontal glass.
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