Bolex Kern Macro-Yvar 150mm Super Telephoto Repair

ic-racer

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I got a good deal on what appeared to be an un-molested Kern Macro-Yvar 150mm super telephoto with the correct mount for my 8mm Bolex.

The rings on the front of the lens appear to have never been touched and the lens elements are clear.

However, at the other end of the lens I found scratches and evidence of multiple assembly and disassembly.

Looks like the 'digital crowd' had their hot little hands on this lens and buggered up the focus mechanism in an attempt to get it to focus on a digicam.

 
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Initial impression was that it DID focus correctly on my camera...but...

 
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ic-racer

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This lens is supposed to be a MACRO and it should rack out to show more of this red band. The red band denotes 'extension factor' needs to be applied to the aperture.

This is as far out as the lens would focus. Only to about 12 feet when the manual documents a close focus to six feet!

 
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ic-racer

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There is something wrong here!

Looks good, right? The infinity symbol aligns perfect with the center mark. But what is the line between 100m and 200m??

Maybe that line is 200m and the line over 200m is the infinity mark.

This suggests it is buggered inside.

Time to have a look...

 
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ic-racer

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The lens is pretty easy to take a part.

How about a shout out to Mikeno62 for providing to me an excellent and careful teardown video of a similar Kern Yvar:
(link below).

Mikeno62's video was great in showing the lens mechanism, but his is not a Macro, so I was still curious why my lens did not focus all the way down to 6 feet even after viewing his video.




 
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ic-racer

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I'll admit defeat here. The focus ring is supposed to make TWO REVOLUTIONS, but mine stops when the two screws hit, just like any other non-macro lens. I was stumped as to how it can make two, but only two revolutions. Because, I can loosen the stop screw and get to the macro range, but then it keeps spinning for more than two revolutions and comes apart.

I had to seek ideas over at the Bolex forum.

 
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ic-racer

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The forums over there are covered by at least two professional Bolex experts. Within minutes I had my answer:

Ball Bearing!
 
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After trying various sized ball bearings, the 2mm fit perfect.

 

Kino

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Well now, isn't that a clever design!

Bolex cameras are interesting, for sure...
 
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Kino said:
Well now, isn't that a clever design!

Bolex cameras are interesting, for sure...
Click to expand...

Yes, I'm embarrassed I did not figure it out for myself.

The Macro Switars also use this ball bearing mechanism to allow the two revolutions of the focus ring.



 

gorbas

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WoW! Congratulation! So, how deep is the adapter from regular C (16mm) to D? (8mm) mount? We had this 150mm lens at our faculty but I don't remember ever using it. Almost all our cameras had standard set 10, 25, 75mm, what was seriously missing is 50mm. It was so rare lens. I think, I have seen one 50mm Switar in the last 45 years. Of course 10 and 25 were used 90% of the time. Maybe 16mm lens will be also handy in the set, also uber rare.
 
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ic-racer

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Very good question.
This lens is made for the H8 REX which has C mount but with a flange-focal length shorter than the standard 16mm C-mount. You can see the difference of the mounts here. The one for the 8mm camera is designated "H8 RX" on the end and is pretty rare.

The H8 RX version of this lens is 2.2mm longer to make up for the difference in camera bodies between the 16mm and 8mm cameras. The rest of the optics are identical between the two versions.

Due to the long focal length, no optic changes were necessary for the reflex prism. So this same lens works on 16mm Rex and non-Rex cameras and also on the H8 Rex (with special mount).

As far as I know, it was never made in a D-mount.

I also have a D-Mount Bolex H8-T but finding any lens longer than 36 or 37mm in D-mount is almost impossible. In fact I settled on this lens for the "Rex" after a lengty search for a tele lens in D-mount. With such a long lens, there is almost no paralax error, so long lenses make sense to me on a non-Rex camera.

 
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I have been collecting lenses for the H8 Rex for some time. I have five of the lenses on this list.

 
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ic-racer

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gorbas said:
... missing is 50mm. It was so rare lens. I think, I have seen one 50mm Switar in the last 45 years.
Click to expand...

I have not seen any in person and this video caught my attentinon not too long ago. Mikeno62 re-lube the helicoid on 50mm Switar he indicated was bargain priced.

 

Kino

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I have a couple of Yvar C mount lenses that take a pipe wrench to turn the focus, so maybe I'll give them a CLA soon.
 
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One last thing. When the lens is affixed to the camera, the index line for focus and aperture is on the bottom. So the lens body needs to be twisted.

Inside the lens, the cylinder with multiple slots serves that purpose. The lens can be re-assembled to always have the index mark on top (or side or wherever) irrespective of the threads on the cameras lens mount.

So, this was simply a matter of loosening the perimeter screws on the focus ring, sliding the lens apart, rotating the body of the lens so the index mark is where I wanted it, and sliding the whole assembly back together.

 
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ic-racer

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When the video above was done, I'm not sure Mikeno62 know about this feature. He could have re-assembled his lens so the index mark was on top.

 

gorbas

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Thank you for update IC-Racer! Interesting that they shared same C mount with slight "but". Until recently I never touched any Bolex D8, only 16mm and strangely I never had desire to buy one for myself.
A few years ago on the camera show I saw this beauty and could not resist. Now it decorates my living room and reminds me of many happy days I spent during my university years with Bolex H16 in my hands. By coincidence I also did film my graduation movie with Bolex 16 Pro.
 
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