Fed 2/50 lens: a coated one???

no news... have you lost hope or is this thing really not working ?

Stephan

Hi Stephan!
I cannot reverse the front part of the lens as it is too curved. Really, I don't know on which body it could work...

Amitiйs. Jacques.

Looking at the Fed lenses: my first guess is that someone substited a front element, possible from a J-8, for one that was damaged. This will be the wrong focal length and "looks good" but will not focus correctly. I was sent a 1951 J-3 all the way from Russia to look at, likewise it would not form an image. The rear glass was "wrong", someone stuck something in from a Planar just to make the lens complete. The front element and front triplet was perfect, and all went happily into a new optical fixture with a slightly later rear triplet.

On this one: if you can measure the focal length of the front element from the working lens, and the diameter of the lens you might be able to find a good substitute. I was able to replace the rear element missing from a Nikkor 10.5cm F2.5 with one from surplusshack.com. "it worked"

I will try to examine it more closely.
The change of the front module, why not?

At this point, how can we explain the cover which is 2mm larger?

Jacques.

It's hard to say what has been done to lenses over 60 or more years. I bought a pre-war 5cm f1.5 Sonnar that was missing the middle triplet and had a front element of 100mm focal length to make the lens a 50mm overall focal length. It formed an image: but had wild distortions.

The early Nikkor 5cm F1.4 lenses have optics and fixtures that are smaller diameter than those made a year or so into production.

I've bored-out the fixture of a Rigid Summicron to replace the front element with one slightly later.

Hard to tell what's been done.

Jacques, did you try it on a zenit 39 ?
It would be very surprising, but why not ...




Stephan

I try to find a M39 Zenit. If not, I will buy one: it's worth trying. It would be crazy: it would mean that Fed was associated to the SLR KMZ work...

Thanks for the idea.

or may be that the 39reflex standard was not a KMZ invention... it's the same frange distance than the M42... and may be the M40... so...

Stephan

Before buying a camera- put a white oiece of paper, or cardboard, on a table under a light. Hold the two lenses to form an image of the light on the paper. If you have to hold the mystery lens "about" 20mm farther from the paper to form the image, and the formed images- might work on an SLR.

If you have a mirrorless camera, might work on it.

The time to find out the lens, and to make other comparisons...
I confirm: there is about 20mm difference between the images with this lens and an ordinary 2/50 Fed lens, all parameters being the same.

But it is with the ordinary lens that the formed image is farther...

It sounds like the lens has mismatched optics in it. The back-focus on the odd lens is much too short to be useful on a camera.

Hello,

I dig out this thread, years after...
At that time, I had no numerics to try this lens. I have just tested it on my Sony , and here is the result:


(opened at f/9)

I am really surprised and I wonder if this lens was made for a special purpose...

Amitiйs. Jacques.