Komura 105 3.5 LTM : infinity focus

raid

raid

Dad Photographer
Local time
9:30 PM
Joined
Nov 2, 2005
Messages
36,603
Location
Florida
View My Gallery
When I today tried out the Komura 105 3.5 on a Canon P, I noticed that at the infinity setting the RF images do no coincide. When switching to a Canon 50/1.2 on the same camera, the infinity RF images coincide.

Does this directly imply that the Komura lens needs adjusting or could it be that it will work well on another camera, such as a Leica M6?

By the way, the lens looks beautiful. It seems to be very well made.
 
Last edited:
Could be either or. My tech says he needs to adjust lenses sometimes.

raid said:
When I today tried out the Komura 105 3.5 on a Canon P, I noticed that at the infinity setting the RF images do no coincide. When switching to a Canon 50/1.2 on the same camera, the infinity RF images coincide.

Does this directly imply that the Komura lens needs adjusting or could it be that it will work well on another camera, such as a Leica M6?

By the way, the lens looks beautiful. It seems to be very well made.
Click to expand...
 
If the focusing cam doesn't project out exactly 7.5mm from the lens' mounting face when focused at infinity, the lens is out of whack. You can just compare it to another LTM lens by mating them back-to-back, pushing one's RF cam against the other's mating face, and vice-versa. Both should just touch.

Probably someone took apart the Komura, and put the focusing helical back together on the wrong start of the threads.

Simple enough repair.
 
Like John said.

On my two Komura teles (I had to lube both of them) you get to the helical like this:

Remove the lens optics from focus mount. Just twist it counter clock wise, like with an older Canon, Nikkor or Jupiter-9.

The focus grip is attached to the helical via 4 brass screws. When you remove those, you can see the helical. Unscrew it, and put it back so that the cam extends correctly at infinity.

All this only if the infinity offset is significant. For very small misalignment, try a very far point first (like a star). These lenses have very long throw (> 300 degrees), and 50m, for example, makes a difference to "real" infinity.

Note also that shimming has no effect on RF infinity alignment.

Best,

Roland.
 
Last edited:
When placing the Komura side by side to an Elmar 9cm 4 which Brian has adjusted perfectly, the two lenses seem to have similar length cams. On the Elmar, when focusing to the minimum focus distance, the focus cam is flush with the mount. On the Komura, the cam sticks out a little. Sorry for the amateurish description.
 
A comparison of infinity focus of the Komura lens on black Canon P [BP] and on a chrome P [CP] reveals that on BP the infinity focus is slightly off but it is fine on the CP. When focusing a Canon 85/1.5 on the BP, infinity focus is fine. It is not the lens or the camera but the matching of this lens on a specific camera. Can this be the reason or am I concluding the wrong thing?

By the way, Eddy Smolov checked both the CP and the BP last year.
 
You can't just eyeball the RF cam depth. Similar isn't good enough, it has to be exactly the same -- the tolerances are extremely tight. The total travel of the cam from infinity to 1 meter focus is all of 2.5mm.

Set this lens and a "known good" LTM lens to infinity focus. Put them back-to-back. Touch the RF cam of the first to the mounting flange of the second, and the mounting flange of the first to the RF cam of the second. The lenses won't line up, they will be staggered, just touching at the 12 O'clock position. The cams and flanges should both just touch each other, with the lenses parallel.

Also, from looking at pictures I have of that lens, it has a very thin tubular brass RF cam. Mount it on your camera, open the back, and open the shutter at T, and see that the RF cam is landing properly on the face of the RF coupling roller in the camera.

If it's a different version with a small RF cam, make sure that the cam lines up with the RF roller when mounted on the camera.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom