Leica M5 Rokkor close focusing issue

[dreilly]

Hey all,
I just bought a Minolta Rokkor-M 40/2 (their version of the Summicron-C made for the CL) and I'm using it on my M5. There's an odd thing happening with close focus: the rangefinder patch seems to go retrograde, that is, it'll move all the one one way, and then move back a bit in the other direction right before it hits the close focusing stop. The cam on the lens appears to have a little notch in it that is probably the cause. I have no idea how this effects close focusing accuracy (haven't shot anything with it) but has anyone heard of this? Is there something wrong?

thanks!
doug

 

[shimo-kitasnap]

hey doug, do you think I could take a look at your rokkor sometime? I'm really liking 40mm at the moment and am pondering the idea of a cron'-c but would like to compare it to my skopar PII.

Are you free anytime after 11am today? I've got a class in coxe at 10.

 

[venchka]

Hmmmmmmmmmm...doesn't this lens do something different on M bodies? Like bring up the 50mm frame? Some folks filed the lens to bring up the 35mm frame. Perhaps your lens was "fixed" by a previous owner?

 

[dreilly]

Bryan, If that's you, sure stop by!

Venchka--It brings up the 50 lines, so it hasn't been changed. I though of doing that, but the 35 lines are at the very very edge of my field of view with my big honking glasses on, so I didn't see the point. I'm wondering is somone might have filed the focusing cam? But I can't imagine why...

 

[venchka]

Hey, I'm clueless. I just buy lenses and slap them on Bigfoot and Bubba. So far, all has been right and proper.

Good luck!

 

[shimo-kitasnap]

yup it's just rf roller cam travel limit. The M5 one sticks out a bit more than other Ms so the little hump at the end of the rokkor's cam re-catches the roller at close focus.

Give sherry a call.......

 

[Palaeoboy]

The cam should be perfectly smooth with no notches in it. The Cam follower or roller doesn't touch the entire cam as the lens has such a short amount of focus rotation. Is the notch on segment of the cam that looks shinier than the rest?

 

[shimo-kitasnap]

it totally smooth and slopes all the way round and right before it ends at the closest focus there it goes back "uphill" about half a centimeter a bit like a plateau. (this is the brass lens cam).

 

[dreilly]

To add to what Bryan said, it's also not brighter than the rest (ie, it doesn't look like someone tried to hack it in any way. Does anyone have a Summicron-C? Maybe it also has the little bump.

 

[Palaeoboy]

No they dont have little bumps at all, can you possibly show a pic of the cam?

 

[dreilly]

images

images

Here are some images of the very pronounced "bump".

Funny thing is that on Bryan's M camera, it focused fine, no retrograde movement.

 

[oscroft]

Does anyone have a Summicron-C? Maybe it also has the little bump

I've just checked mine too - no bump

 

[former member]

Who the hell put that bump there!

I've seen some damaged RF cams on lenses. I've even repaired a couple with copper tape. It looks like someone had a focus problem with the lens and decided to "correct it". I would check the accuracy of the focus throughout the range. At some point, there will be a discontinuity.

Or on the other hand- maybe it corrects focus shift at close-range, used wide open...

 

[oscroft]

Has that cam been ground down over most of its length, with the "bump" at the end being left at its original height?

 

[Paul Connet]

Here are some images of the very pronounced "bump".

Funny thing is that on Bryan's M camera, it focused fine, no retrograde movement.

I do not have a Rokkor 40mm, but I do have a 35 Summicron and a 50 Summicron that both have a slight "bump" similar to the pics of your lens. It seems to be at the end of the cam grind slope and on both of my lenses it is far enough away from the point that the lens focus stops so as to have no effect. I would suspect this is normal and that on your particular lens the cam grind was simply not carried far enough past the focus stop point.

Regards, Paul C.

 

[shimo-kitasnap]

Hey Doug, why don't we wait until I get those shots developed of the test that I did at full aperture in your office and then decided if there's a problem or not. How's monday sound?

 

[shimo-kitasnap]

Doug, don't worry it's normal, i just saw the same thing on a 40 rokkor on the evil bay. Same flat hump thing right at the close focus. I wouldn't worry about it now.