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Repairing M-Hexanon 90mm f/2.8 Backfocus on M3
Old 05-15-2010   #1
bwcolor
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Repairing M-Hexanon 90mm f/2.8 Backfocus on M3

I just purchased this lens via Ebay. Tight head to torso shots at f/2.8 show a good bit of backfocus. I asked Sherry if I can send the lenses to her and she says that she doesn't do that type of work. Is this a home-repair? If not, where do I send the lens and should the M3 also be sent at the same time?
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Old 05-15-2010   #2
mathomas
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Interested in the answer on this. I have a similar problem at close range (have only shot it on my M8 though, no opportunity yet on my M2). On the other hand, the M-Hexanon blows away my old Elmar-C on long-distance shots (and the Elmar was no slouch, of course).
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Old 05-16-2010   #3
Uwe_Nds
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I had the four M-Hexanons and all of them didn't focus properly on the M8. Same issue as with yours.
Talked to Mr Reinhardt, a very highly regarded repairman in Hannover, and he told me that despite previously being the Konica RF-service point in Germany, he couldn't adjust the lenses.

So I sadly sold them.

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Old 05-16-2010   #4
Chriscrawfordphoto
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I think some people on RFF have had Don Goldberg adjust Konica lenses. You might call him. He adjusted some leica lenses for me and they are perfect now. I think I've seen people here say he did their Konica lenses.
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Old 05-16-2010   #5
Ezzie
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Konica never would clearly state if the M-Hexanons indeed where 100% M compatible. I guess Iīm lucky in feeling my 90/f2.8 seems to be performing OK (on the R-D1).
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Old 05-16-2010   #6
ferider
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For the OP: what other lenses have you used on your M3 ? Does the 90/2.8 Hex perform at infinity ?

Roland.
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Old 05-16-2010   #7
ampguy
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The M-Hex 90 is a Sonnar type design, so if you do have it adjusted or optimized, it will likely be for only a few f stops range.

Do some focus bracketing at different apertures close up and at infinity and see at which apertures it is backfocusing, and where it may be spot on or optimized already for.
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Old 05-16-2010   #8
Brian Sweeney
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I fixed the back focus on the 10.5cm F2.5 Nikkor by putting one piece of copper tape of the RF cam.

What does the RF cam of the Konica look like? The Nikkor uses the "Tongue" type cam.
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Old 06-02-2010   #9
bwcolor
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I've primarily been using the Leica apo/asph 90mm and it seems to be spot on with the M3...even at f/2.0.

The aperture issue with the Sonnar design has me thinking that I need to go back and do as suggested..testing at various apertures.
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Old 06-02-2010   #10
ferider
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One more question: how does the lens behave at infinity ? Is the RF aligned and is it sharp (not too different to your Leica 90). If the RF "over-shoots", meaning the camera shows you infinity earlier than the lens, a simple shim under the lens mount might do.

Also, do check with Don, I believe he works on M-Hexanons.

Roland.
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Old 09-08-2018   #11
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Old thread but I just picked up a M-Hexanon 90mm and it was back focusing on a m240. The rangefinder on the camera is almost spot on when used with a DAGd Summicron and a new Voigtlander 28mm Ultron.

Checking at the infinity lock the lens seems focused correctly so I assumed it was the RF section of the lens that was slightly off. Turns out this is fairly easy to adjust.

https://jrhughes.wordpress.com/2015/...f2-8-part-two/

Basically you remove the mount from the lens and then use a lens spanner to remove the collar for the RF cam. Lift the cam out and there will be a number of shims. I used very fine tape on one of the shims to make it thicker and then reassembled it. Watch out for the pin the cam engages in to make sure you don't knock it loose. When reassembled the camera was front focusing so I took it apart again and removed (2) .002mm shims and now it is just about spot on.

Shawn
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Old 09-08-2018   #12
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Quote:
Originally Posted by shawn View Post
Checking at the infinity lock
The Hexanon-Ms donít have an infinity stop and are designed to be able to focust past infinity. You need to focus to infinity to adjust them for focus.

Of course if your adjustment works, it works, just be aware that this approach is at least potentially capable of causing problems.

Marty
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Old 09-08-2018   #13
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Thanks for the info, that is interesting. The lens stops right at the infinity mark, not past it. The focus scale distances are also accurate.

Shawn
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Old 09-16-2018   #14
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Quote:
Originally Posted by shawn View Post
Thanks for the info, that is interesting. The lens stops right at the infinity mark, not past it. The focus scale distances are also accurate.
How are you measuring infinity? On an optical bench, my 28 and 50mm Hexanons focus well beyond infinity and the 90mm a little beyond, but more than enough that with the focus against the stop photos are at f5.6 of distant objects are soft.

Marty
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Old 09-16-2018   #15
shawn
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The moon wide open at the infinity stop is sharp.

Edit: Clear night tonight so I just tested this again. Both shot wide open. Left side is at infinity stop, right side is rotated ever so slightly in from infinity. This is zoomed in to 4:1.

Both were defringed in Lightroom as the lens was fringing strongly along the edge of the moon.

Shawn
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Old 09-17-2018   #16
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Quote:
Originally Posted by shawn View Post
The moon wide open at the infinity stop is sharp.

Edit: Clear night tonight so I just tested this again. Both shot wide open. Left side is at infinity stop, right side is rotated ever so slightly in from infinity. This is zoomed in to 4:1.

Both were defringed in Lightroom as the lens was fringing strongly along the edge of the moon.
Thanks, these look right. You know at least itís not focusing past infinity. Thatís good; as I said, mine were all off.

Marty
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