Quick Exakta lens to Nikon F adapter

overmywaders · Joined: 27 May 2009 Posts: 49

I have been trying for some time to bridge the 1.8mm gap between the Exakta mount lenses I like and the Nikon DSLR I use. After many different approaches, some requiring removing the Nikon flange, I am still about one mm away from infinity.

However, I thought I would share a simple, inexpensive, and quick method for mounting the Exakta on a Nikon F and enjoying, if not infinity, at least great usability.

You need the following:
one Nikon camera with F mount
one Exakta lens with standard Exakta bayonet mount (not Real)
one rubber O-ring 2mm thick and approx. 38mm in diameter
one M39 (LTM) to Nikon F adapter
one jeweler's slot screwdriver
and 1.5 minutes

Below are the components. Exakta mounts are 38mm in diameter; the LTM is 39mm, but the threads make it less.

First, remove the stop pin from the lens mount and save it. If you wish, you could instead drill a hole in the adapter for the stop pin.

Drop the M39 adapter over the Exakta mount, it will fit easily but not sloppy. Turn the adapter until the projections of the Exakta are between the projections of the F-bayonet. This allows you to insert the 2mm thick O-ring into the notch under the Exakta bayonet. Stretch it and poke it into place.

This is the final result. The fit is such that it would be difficult to pull the lens out of the adapter. Now mount the adapter on the Nikon, just as you would a Nikon lens.

While this adapter adds one mm to the 1.8mm difference between the Exakta flange focal distance and the longer Nikon FFD, it does allow good use of the lens. These photos were taken with a Meritar 50 2.9 so mounted, with no flash and in low light. The minimum distance is reduced from 0.8m to 0.5m.

Regards,
Reed

luisalegria · Expire: 2018-01-18

Clever one, thanks.

It seems to me that a more secure and permanent (yet still non-destructive) fix is possible along these lines, a true Exakta-Nikon adapter, if the M39-Nikon adapters are easily found and can be "sacrificed".

overmywaders · Joined: 27 May 2009 Posts: 49

Luis,

They are readily available on the 'bay for less than $10.00US

Click here to see on Ebay

Click here to see on Ebay

Click here to see on Ebay

The connection provided by the O-ring is very strong. I cannot separate the lens by a straight pull. Plus the rubber O-ring keeps the lens tight against the flange. For a particularly heavy lens you could step up to a 2.5mm thick ring; though I don't find that necessary.

Regards,
Reed

Gurdie · Expire: 2013-02-20

Under our house is a storage space, not a real cellar, filled with old furniture etc. I knew, that somewhere there was an aluminium barrel camera lens, used in a home-made enlarger and left there when moved in about 20 years ago.

One day I rummaged there and found the lens, an alu 50/2.8 Tessar, as I had believed it to be. As the lens bayonet is a 3-wing type, I thought it was an Exakta mount.

As I had a M39-Nikon adapter, I tried this o-ring adaptation, but my lens doesn´t fit like in your pictures, the bayonet wings are way too wide to get inside the M39 threads. They don´t fit inside the M42 adapter either.

Is my lens some other mount?

The lens with the M39 adapter

luisalegria · Expire: 2018-01-18

That looks like a Praktina mount

Gurdie · Expire: 2013-02-20

Thanks, Luis. It sure looks like a Praktina mount.

Maybe I could try that with a M42-Nikon adapter, if I file the bayonet wings just a little. The lens is not worth much, I think.

overmywaders · Joined: 27 May 2009 Posts: 49

If it is a Praktina mount you won't have much trouble getting infinity as the flange focal distance is greater for the Praktina than the Nikon F. You are lucky, I'm still a millimeter away with my Exaktas.

Gurdie · Expire: 2013-02-20

My Tessar doesn´t focus to infinity even without any adapter on my D200.
If I put the lens against the mount flange, the lens focuses only to 3-4 metres. Strange. If I understand right, a Praktina lens should focus past infinity on Nikon body without any adapter, because the register distance is greater than Nikon´s.

xoxixox · Joined: 29 Mar 2009 Posts: 83

Hi all,
I have severals Praktina lenses, and none of them can focus at infinity on my Nikon nor my Canon. I think the info that the Flange distance of 50mm is untrue, well is misunderstand :
Effectively, the distance of the metal ring of the rear of the lens to the film plane is 50mm, but the rear of the lens go inside the camera for about 14,55 mm !!
I thing the flange distance as to be measured from this point so 50 - 14,55 = 35,45mm. It's too short for Nikon F and for Canon EOS !

luisalegria · Expire: 2018-01-18

Most lenses go in a little bit into the mount from the "flat" from which the back focus distance is measured, sometimes 5-8mm

The Praktina mount is an extreme case, but that doesn't mean an adapter can't be made. The advantage of the Praktina is that there is so much room to work with.

I have seen a custom-made Praktina adapter in the other manual focus group, so it is possible - this gentleman made one for his Canon 5D -

http://forum.manualfocus.org/viewtopic.php?id=9596&p=2

His adapter looks like there is room to make one for a Nikon also, it just needs to be 2mm thinner.

Jieffe · Joined: 04 Nov 2007 Posts: 754 Location: Belgium

I managed to convert (with full reversability) my Praktina Trioplan to Pentax K mount.

I removed the mount and replaced it with a (cheap chinese) Pentax K extension tube. I had to increase the thickness of the lens with electrician tape and wedge it into the tube but it works ...

If I had kept the original mount, the lens couldn't reach infinity.

xoxixox · Joined: 29 Mar 2009 Posts: 83

Pancolart · Expire: 2013-11-18

Gurdie · Expire: 2013-02-20

sajualex1 · Joined: 11 Sep 2011 Posts: 40

I got the M39 adapter today, now waiting for the O ring. i hope that i can receive it very soon.. Smile

sajualex1 · Joined: 11 Sep 2011 Posts: 40

At last i mount the mayer trioplan on a Nikon D40, not yet tested. Will post the snaps later. Thanks for the M39 adapter idea. Smile

mmmio · Joined: 04 Apr 2010 Posts: 4

it is good too for Canon EOS 5D mark I Mount or only for nikon?

Lena · Joined: 24 Apr 2012 Posts: 495 Location: Pl

Which would be easier to mount on Nikon: Exakta or Praktina? I don't necessarily have to get infinity, but the working distance I get with M42 lenses would be nice.

Lena · Joined: 24 Apr 2012 Posts: 495 Location: Pl

Eventually I got the Exakta version. I replaced the bayonett with the thinnest macro tube + Nikon mount from the tube set and somehow I have infinity focus Shocked

The problem is I can't stop the lens down, but I will play wide open for a while and see what to do next.

It worked with the black Trioplan N.

Attila · Expire: 2025-11-18

This is a good news!

johjeff · Joined: 14 Aug 2013 Posts: 20

Lena,

Do you have links to the products you used to mount the Exakta lens on your Nikon? I just won a Carl Zeiss Jena Nr.3379720 Tessar 1:2.8 f = 50 mm Photo Lense on ebay, which has this mount:

Which I have been told is the Exakta 35mm mount. I have a Nikon F-Mount camera and would like to use this lens.

Thanks for your help.

johjeff · Joined: 14 Aug 2013 Posts: 20

I am a little confused by where exactly the front element of the lens should be in relation to the opening of the Nikon body. Should the lens be more inside, or more outside the camera body to achieve the full focal range?

Also, is infinity focus really that important for most landscape or people shots?

Does anyone have some examples of using the m39/0-ring mod using a CJZ tessar 50 2.8?

Thank you.

mcwc · Joined: 14 Feb 2014 Posts: 1 Location: Vancouver, BC

Has anybody else tried to mount an Exakta lens to a Nikon F-mount body? I have a Flektogon 35mm f2.8 that I would like to use on my Nikon D600 and hopefully with infinity focus.

I was thinking of using a variation of the method used by OP and what the Pentax K-mount guys have tried.

This is what I'm thinking:
- Thread on a M39 to M42 adapter ring & lock into place with an o-ring. I would prefer not to use glue if I don't have to.
- Screw on a M42 to F-mount adapter. Test for infinity focus.
- If it doesn't focus to infinity, grind the M42 adapter to make it thinner. Test for infinity focus. Repeat grinding if necessary.
- Test for interference with the reflex mirror on a camera with a mechanical mirror lock-up such as a Nikon F4.
- If everything works out, then I'll use blue thread locker between the M42 to F-mount adapter and the M39 to M42 adapter ring.

luisalegria · Expire: 2018-01-18

On its own, unless you are lucky in that the lens already focuses way past infinity, you will not get infinity that way.
Even a zero-depth adapter will still be more than 2mm over minimum back focus.

Speaking from the PK side, which is 1mm closer to the magic number than the Nikon world, I have found NO Exakta lenses that can be mounted on a similar adapter that give me infinity (and I have had several dozen Exakta lenses), unless adjustments are made to the lens itself - i.e., setting back the position of the lens block, adjusting the helical travel and limits, etc.