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Leica Tales from the Greasy Side: Komura 105mm F3.5 Teardown.

BrianS

Super Moderator
Apr 3, 2013
124
This thread will be continued as I try to bring this lens into working order.

For now- the teardown, as I could not find this anywhere on the web. This is a fairly uncommon lens in Leica mount. It is similar in construction to the 135mm F3.5 Komura that I relubed- and learned some lessons with. Like: DO NOT SEPARATE THE HELICAL! Too hard to get back together.

The Optical Barrel separates from the focus mount, but this one was very stubborn. A rubber sheet was required to grab the front of the lens and the aperture ring.

Komura105_barrel_out by fiftyonepointsix, on Flickr

The chrome trim ring unscrews from the focus ring.

The optical barrel also screws into two sections allowing access to the surfaces on each side of the aperture. The middle group will also come out of the front section, but this was not necessary for this lens.

Komura105_focus_ring_split2 by fiftyonepointsix, on Flickr

The focus ring is in two sections, I use a silver sharpie to mark positions. Undo the set screw, unscrew the distance ring from the front section.

The front of the focus ring is held in with 3 flat-head screws. Take them out, the focus ring comes off.

Now you can extend the helical for cleaning.

This is about as far as the helical can be extended without separating it.

Komura105_Helical_exposed_MAX by fiftyonepointsix, on Flickr

"Do you feel lucky" in re-assembling? After my experience with the 135/3.5: I am very good at getting these back together. But not THAT lucky. I used acetone to get the old grease off using Q-Tips and paper towels. Held the helical over a pyrex dish, flood cleaned the best possible. Then used white lithium grease, focus is very smooth now.

This lens has a problem: the focus and RF do not agree, and the optics cannot be screwed far enough into the mount to correct the problem. I would have to grind the end of the helical down, and grind down the chrome trim ring. As this is a telephoto lens, I am going to use a shim on the M-Mount adapter instead. The idea is to back the RF cam out just enough for the focus to agree at ~5m. The actual focus of a 105mm lens will not be dramatically affected by a 0.2mm shift, which is about what is required to correct the RF. Will report back later.
 

M. Valdemar

Veteran
Aug 5, 2013
104
New York City
I had one of these, plus a Komura 85mm f1.8 in Leica thread. I sold both of these for relatively little money.

In hindsight, perhaps foolish. But I did OK on the 85mm f1.8 when I sold it.
 

BrianS

Super Moderator
Apr 3, 2013
124
I paid under $100 for this one, inclusive of shipping. The canon 100/3.5 is smaller and sharper. The Nikkor and Canon 135's are sharper than the Komura, which I picked up for $50. These are decent lenses, "obscure" compared to others. But- I would not pay more for them than any Canon or Nikkor lens.
 

BrianS

Super Moderator
Apr 3, 2013
124
I finally got good agreement between the RF and actual focus. Added a 0.1mm standoff shim between the lens and the M-Mount adapter. This corrected the error between the distance measured by the RF and actual distance to the object at 5m. With the distance and RF in agreement, the lens still had a slight front-focus. I removed the 0.15mm shim from the optics module and screwed it as far as it would go into the focus mount. The agreement is "good enough". I'll be testing it when the weather cooperates. Overall- this lens is lower contrast than expected, soft wide-open, and definitely lacking in calibration to the Leica. This lens was not mis-assembled on some prior repair, all taps for set screws line up perfectly and there are no "extra taps" as would be present if the lens was modified before taking it apart. If this lens was used before- someone calibrated the RF of the camera that it was used on for this lens.

Worth $100 with shipping? The optics are good, now any minor haze is cleaned out. It's an uncommon lens, but not one that would be searched out for it's optical qualities. It is big and heavy compared with the Canon 100/3.5 and Minolta 85/2.8.

Worth the ridiculous prices that sellers on Ebay ask for it? No. The Minolta 85/2.8 can be bought for less, is a much better lens. Mine was spot-on for focus. A clean Canon 100/3.5 would be a better choice, but one with perfect optics is hard to find. The Nikkor 10.5cm F2.5 is faster and sharper, a bit heavier- goes in the $300 range. With that in mind, the Komura is worth the $100 paid, about the same price as a clean Elmar 9cm F4.
 

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