Zorki-6 + Canon 135mm f3.5 Focusing

[nation_of_pomation]

Hi all,

I recently acquired a black Canon 135mm f3.5 lens (which I think is a later one, since the elements remove from the barrel to work with a mirror housing unit) and I purchased a Z-6 shortly before, and I attempted to use the lens as the last few test shots on the first test roll. I missed focus on every single shot, as I made sure I used f8 or larger to keep the focus shallow to check it. To me, they look like they were focused past the intended subject. Could it be A.) the fact that I tried focusing first, then looking through the accessory turret finder when firing the shutter B.) an issue with the lens itself or C.) a combination of long focal length and an inaccurate rangefinder? I bought the Z-6 from Yuri at fedka.com, so I know the RF was adjusted and working perfectly when I got it. The shots I took with the Canon 28mm f3.5 and f2.8 and the Jupiter-8-1 on the same roll all seem to be acceptable to spot on. Any thoughts?

 

[nation_of_pomation]

Examples

Examples

Here are the 3 test shots from the end of my test roll with the Z-6:

You can see the focus is off the grass in the center and much closer to the one off to the right.

Here, the focus is past the little weed I had focused on and instead on the edge of the wood frame.

And in the last one, it's actually a little short and is on the bit of rope off to the right instead of the knot tied around the rose vine.

Any thoughts?

 

[ZorkiKat]

Is the focus coupling tab engaging the camera's rf cam properly?

AFAIK, the long Canon LTM's used a tongue-shaped tab which must engage with the camera's tab completely. If the camera rf cam engages with the edge of the lens's coupling tab, the focus may not be correct.

Or you may have to check the camera's rf adjustment for 1 metre. A Zorki RF which is correct at infinity is not necessary correct for the minimum focus distances.

 

[Spyderman]

Another reason could be the famous Leica - FSU incompatibility. FSU cameras assume the movement of lens as if it was a 52.3mm (inherited from pre war Zeiss Contax lenses), while Leica and compatible cameras assume 51.6mm lens. Simply said between the Canon (built to Leica standard) lens and say Jupiter-11 135mm/4 (FSU standard) the lens RF coupling cam moves different amount for the same focussed distance (and the other way round for the same movement of the cam, the lens is focussed at different distance). At infinity they are identical, but as you focus closer the difference gets larger.

However even this incompatibility can be overcome by different adjustment of the camera RF coupling arm wedge (the part at the end of the arm, which contacts the lens). Go take a look at ZorkiKat's Zorki survival site.

 

[ZorkiKat]

The only true compatibility issues I've ever encountered with Canons on Zorki or FED -aside from the mis-adjusted RF follower cam- is the non-standard lens thread and lens mount positioning.

I don't see the FSU vs Leitz incompatibility as a constant factor. It's more of how the lens mount was placed and threaded.

The threads on the lens mount of the Zorki or FED do not match the start and end points of the Leica-standard (including Canon). Leitz and Canon (and even the copies like Nicca or Leotax) made sure that their lens mount flange threads started within 5º or so, more or less, in the same place. Goes to say too that the threads stopped at exactly the same places. If not they'd had trouble with the Hektor or long Canon lenses whose coupling cams were not full barrel, but instead tongue shaped. The bar on which this coupler was mounted had to stop precisely in front of the camera's rf coupling cam.

This was not so with many FED or Zorki. In fact the tongue-shaped lens cams could be potentially damaging (to both lens and camera) in some examples. The cam can get stuck to the camera's focus follower.

Another reason for improper focusing is the placement of the lens mount. Often, when the camera gets serviced and its lens mount is removed, the fine adjustment which put the lens flange mount exactly 28,8mm from the focal plane is upset. It does not take much to lose that adjustment and a discrepancy of just 0.1mm is more than enough to cause the focus to shift.

On the other hand, in the FED and Zorki which I have whose lens mounts are "properly" threaded (by Leitz standards), spaced correctly at 28.8mm, and with properly adjusted RF focusing cams, will focus both Soviet lenses and Canon lenses. My 2/85 Serenar Canon focuses properly as well as the Jupiter-8s which interchange with it.

 

[nation_of_pomation]

So, because of design specifications, a Jupiter-11 might engage the RF cam better than the Canon? My version is definitely that with a RF tongue/tab instead of an all-around protrusion to engage the rangefinder. What do you think the best way to test the compatibility of my sample of lens with my sample of body?

 

[wolves3012]

So, because of design specifications, a Jupiter-11 might engage the RF cam better than the Canon? My version is definitely that with a RF tongue/tab instead of an all-around protrusion to engage the rangefinder. What do you think the best way to test the compatibility of my sample of lens with my sample of body?

Jupiter 11 has a full-circle RF cam, like a tube. For that lens, it cannot engage incorrectly against the RF sensor. For the tongue variety, the RF sensor can become locked by dropping below the tongue. On a Zorki 6, you have the option to open the back, remove the film (if any) and physically disengage the sensor. On a bottom-load camera, you can't do that and you have one serious problem.

For your Zorki 6, you can mount the lens and leave the back open. Move the lens over its full focus range and observe the RF sensor through the open back. If the sensor never reaches a position to jam, even when mounting and un-mounting the lens, you're safe to use it. If it's even close to going beyond the tongue, don't risk it in use or you'll probably have to remove the film to get the lens un-jammed. I suspect you'll find it will not be usable.

 

[nation_of_pomation]

Okay, so I just tried what you said in re: to the rangefinder cam engaging the tab on the Canon 135mm f3.5, and when it was fully mounted and flush against the base of the lens mount, the tab sat with the cam flush against it. The left half of the tab is what makes the connection, though, so it isn't centered. I can post a photo if that description doesn't make sense. The cam doesn't slip under the tab, though. Also, if you think it will help to compare, I can get a J-11 and compare it on the Zorki-6 to the Canon lens.