Konica Hexanon-M 90mm Focus Issues?

[danieldouloslee]

I just got a 90mm Konica Hexanon-M (Leica M mount) lens. However it seems like it is having focus issues on my M262; perhaps back focusing. I shot this photo at 2.8 and focused right on the letters. You can tell that it is very blurry/out of focus. I have added a few other photos, and I believe are shot at f4 and 5.6. All are incredibly not in focus.

I am fairly confident that it is not the rangefinder's fault as my 50mm is tack on sharp. Would anyone know what the issue might be? Would it need a calibration?

 

[shawn]

What shutter speed where those at? Hard to tell at those small sizes but on the bottle picture it doesn't look like anything is really sharp which suggests a bit of motion blur.

The 90mm can have its focus cam adjusted pretty easily with spacers. I tweaked mine slightly after I got it. Take some shots of the moon at the infinity stop and check the rangefinder. In my case the RF was off a little but the shots were sharp. On the lens remove the lens mount and unscrewing the RF cam I was able to remove a brass shim to get the RF cam on the lens in better shape.

Lens can be *very* sharp but not harsh at the same time.

Shawn

 

[danieldouloslee]

Hi Shawn, beautiful photo and sharpness! Which camera do you have the lens mounted on?

Not sure why I have such haziness. Perhaps my lens is a dud. Regarding your question about Shutter Speeds:
Bottle: 1/125
Street Sign: 1/3000
Happy Birthday: 1/30

Can you show me how to change the lens focal with spacers? I'm not sure if I am following.

 

[peterm1]

The best bet is to start by testing it yourself.

This is much easier to achieve with a digital M so you are lucky. Here is how I did it when I had problems with my M8 (which were with the rangefinder calibration not my lenses). I took a 1 meter length of wood and clearly marked a focus point target in the centre of it. Then either side of the focus point and at 1 cm intervals I marked a dozen or so indicating points which are intended to show if the lens is front focusing or back focusing and by how much.

I then laid the wooden test piece on the floor and placed the camera nearby on a tripod a measured distance from the central focusing point. The measurement has to be made using a tape measure and be measured to the plane of focus (usually marked somewhere on the camera body but it can be estimated in any event). I used 3 meters as the measured distance as it was convenient and the lenses I tested also had this marked on the focusing scale. You can use any convenient distance that works for you.

Then take a test photo using the rangefinder and then another using the focusing scale on the lens (which is why you need the actual distance to the target to match an indicated distance as per the markings on the lens). If the focus is off (i.e. either a marked spot in front of the focus point or a marked spot behind is sharper than the intended focus point) you have just confirmed that there is a focusing problem. If the image of the focusing point is off using the rangefinder this suggests that the problem is the rangefinder calibration of that lens. If the focus is off using the focusing scale and especially if there is no point of sharp focus at all using the focusing scale, it suggests some optical issue or some other problem.

Repeat the experiment with another lens. If the focusing is accurate with the other lens this confirms that the problem is with your Konica Hexanon not with the camera body / rangefinder. If both are off this suggests a problem with the camera body.

In my case the problem started suddenly with no apparent cause...no bumps etc. I still do not understand why. The point is this can happen quickly with no obvious cause so being meticulous is a useful technique to ID what corrective measures are needed.

 

[Doug]

During the time of early production of the Konica RF camera there was apparently a discrepancy (and a controversy) over a possible difference in the lens flange to film register distance from "Leica standard". This may well have also affected Konica's Hexanon-M lenses then. Just a thought to give a bit more weight to the idea of having the lens checked and adjusted as necessary.

 

[shawn]

Hi Shawn, beautiful photo and sharpness! Which camera do you have the lens mounted on?

..... Can you show me how to change the lens focal with spacers? I'm not sure if I am following.

Thanks, that was on a M240.

All this is assuming the cameras RF is accurate. I have a DAG'ed Summicron that is my reference.

On a RF lens there are basically two different things that need to be accurate on the lens for accurate RF focusing.

The optics themselves need to be positioned properly and the lenses RF cam (the thing that moves the RF in the camera) also has to be positioned correctly.

On my 90mm if I focused at the infinity stop the RF in the camera was actually slightly past infinity. I wasn't sure if the lens was off optically or if the lens RF cam was off.

I checked the optics by putting it on the infinity stop and then shooting the moon. The moon was very sharp at the infinity stop. If I took a shot with the RF looking properly focused the moon was hazy. That told me the optics were accurate and that the RF cam in the lens was off.

The cams position is adjusted by brass shims. I need to make these ever so slightly thinner as the cam sticking to far into the camera. To get at the shims are easy. Remove the screws on the lens mount itself.

Once that comes off you will see a collar around the cam that moves in/out with lens focusing. There are two holes on it for a lens spanner to fit in. It simply unscrews. Once the collar is off the cam will lift right out and the brass shims are under it. There were several on my lens. In my case I had to remove several shims (micrometer is very helpful here) and a combination of a additional shim material to get the lenses RF cam to all work out at infinity. I also tested focus at closer points and it ended up being very accurate.

This site explains it but doesn't show the lens apart.

https://jrhughes.wordpress.com/2015/04/12/konica-m-hexanon-90mm-f2-8-part-two/

Mechanically the procedure is very simple. Just a little trial and error as you will probably be taking it apart a few times to get it dialed in. Live view and the EVF really helped speed this up on the M240.

If the lens is off optically (moon OOF at infinity) than the optics in the lens will need to be adjusted. I haven't done that so I can't help there. I haven't been able to find the service manuals for the M-Hexanon lenses.

Hope this helps,

Shawn