Canon 85mm f1.9 LTM disassembly

[shawn]

Hi,

I recently picked up a silver Canon 85mm f1.9 that is in excellent shape.

The rear element had some haze but it cleaned out nicely as I was able to unscrew the optic block.

The helicoid is a little stiffer than I would like so I would like to regrease it. Not sure how that comes apart though.

Any tips or tricks appreciated.

Thanks,

Shawn

 

[Mackinaw]

I haven't tried to take apart this particular Canon rangefinder lens, but have taken apart several others in order to clean. Most are relatively easy to take apart and reassemble. For your haze issue, try coming in from the back. Removing retaining rings and such is pretty logical. Take your time and take pics. The stiff helical is another matter entirely. I've never tried that, so no comment. Good luck.

Jim B.

 

[shawn]

Thanks Jim. I figure out how to take it apart.

Optics are easy from the front as the whole module with aperture just unscrews from the front. Then the rear optic unscrews from that module.

Taking apart the focus ended up to be fairly easy, getting it back together was a little more of a puzzle. The distance scale on the lens has one set screw. If you take that screw out and then unscrew the distance scale (it is separate from the focusing ring) you can unscrew the two halves of the helical. When I had them apart it was easy to clean and regrease one side. The other side would have take more disassembly but I didn't need to go that deep.


The mount area has three set screws. Take them out and the entire mount with DOF scale will come out. Leave this off to reassemble the lens.

The distance scale and the DOF scale have each part of the focus limiter in them. I found it easiest to put it back together by screwing the distance scale completely into the focus ring and putting in the set screw.

There were two scribed lines on the brass body (mount side) that lined up the helical with the set screw hole in the focus ring half of the assembly. Line those up to get the helical started.

Then lining up the helical and screwing it together. Make sure the RF cam is fully extended when you have the helical all the way together. You might need to reach into the lens body to hold the spring loaded actuator out slightly to get the helical to screw in all the way.

After you have that screwed in all the way I back off from infinity slightly (to give room around the focus limiter) and then put the mount/dof scale back on the lens. A little tricky to get the three holes lines up but I used wood toothpicks in them to get it all lined up.

Could probably take it apart without removing the set screw on the distance scale. If you just take off the mount/DOF scale that would disable the limiter and allow it to unscrew completely. Taking out the distance scale gives a little more access to outer side of the helical to be able to clean it more.

Shawn

 

[shawn]

Have to update what I said above. I wrote the wrong starting point for the helicoil. It actually starts just below the 4' mark if the focus ring is connected to the focus ring. Pictures attached with the DOF scale removed, and the marks on the inner body to reassemble the helicoil.

Make sure you remove a LTM to M mount adapter or you won't be able to get the DOF scale off.

Shawn