Backfocus Adjustment

[atufte]

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I've got a Summicron 35/2 pre-asph with slight backfocus, is there any way to fix this your self...? It's very little, but enough to set me off when shooting portraits up close,( when i focus on the eyes @ f/2 the side of eye (temple) will have the exact focus point, so it's off by 0.5-1 cm) It seems fine on infinity...

[jayproth]

Check out this thread!

http://www.l-camera-forum.com/leica-forum/leica-m8-forum/13933-new-backfocus-thread-solution.html

 

Most people find it risky, and its not a fix for a badly focusing lens but I had problems with front-focus on all my lenses and after messing with the cam (as detailed in the thread) and a noctilux at different apertures, I got all my lenses to focus well.

 

It helps if you hook up the M8 with the eyepiece magnifier to a tripod and to your computer and use Leica Digital Capture to evaluate the shots.

 

Hope this helps!

[atufte]

Thanks, but i don't think adjusting the RF on the camera would help me, since i have at least four other lenses which works perfect...i have to adjust the 35 lens only, if possible...?

[markku]

howdy!

 

Same here. I got my M8 in May, finally after waiting for 9 months, like waiting a baby they say

Well you can imagine how I was feeling, first carefully unpacking, being proud of my new toy... and yes in my cousins graduation party I only managed to get two pictures right on spot. They were incorrectly focused. The others correctly focused were back focusing by a meter or two on 30-40 meter distance. This was disappointing:(

 

Well further investigation proved that 50mm apsh lux and 75 asph cron were back focusing. My 35mm cron asph and 21mm pre-asph weren't.

 

Lucky me I thought right by not sending them back to Leica but rather I managed to adjust the focus by using allen wrench and turning a notch to left. That helped. All my lenses focus now correctly, almost. The 50mm lux back focuses only about 1 cm at short distance.

 

I'm totally happy with this solution and even more that I know I don't need to wait several weeks my whole package being in Solms...

 

The reason for wide angles not back focusing and after adjustment still being in focus must be due to that their DOF is so much better especially being cron and elmarit.

 

/markku

[atufte]

howdy!

 

Same here. I got my M8 in May, finally after waiting for 9 months, like waiting a baby they say

Well you can imagine how I was feeling, first carefully unpacking, being proud of my new toy... and yes in my cousins graduation party I only managed to get two pictures right on spot. They were incorrectly focused. The others correctly focused were back focusing by a meter or two on 30-40 meter distance. This was disappointing:(

 

Well further investigation proved that 50mm apsh lux and 75 asph cron were back focusing. My 35mm cron asph and 21mm pre-asph weren't.

 

Lucky me I thought right by not sending them back to Leica but rather I managed to adjust the focus by using allen wrench and turning a notch to left. That helped. All my lenses focus now correctly, almost. The 50mm lux back focuses only about 1 cm at short distance.

 

I'm totally happy with this solution and even more that I know I don't need to wait several weeks my whole package being in Solms...

 

The reason for wide angles not back focusing and after adjustment still being in focus must be due to that their DOF is so much better especially being cron and elmarit.

 

/markku

 

Thanks, but how can i adjust the RF with the allen on the camera, without loosing the perfect focus on all my other lenses....?

[charlesphoto99]

Thanks, but how can i adjust the RF with the allen on the camera, without loosing the perfect focus on all my other lenses....?

 

If all (not sure how many or what those lenses are) the others focus properly, then it's probably the lens itself that needs adjustment and not the rangefinder. Send to Solms or better yet a reputable Leica lens repair person for less wait and money (sorry, I only know US and that is DAG).

[B&W]

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Alexander, I do believe Solms is the place to send it to

[atufte]

Alexander, I do believe Solms is the place to send it to

 

Thanks, i really hoped i could get around this without sending it away for weeks (or even worse, months) but if the only solution is Solms, then Solms it is... :-(

[markku]

I hesitated as well as two of my lenses seemed to be OK and two far from it.

I've always been a bit curious person, so I had to try and see what happens. And especially if you remember how much you've turned the key and to which direction you could always go back to original setting:)

 

So I tried and the situation now is a lot better as my wide angles are still OK but 50 and 75 don't back focus anymore.

 

It is 100% sure that the focus plane has moved on every lens but lucky me it isn't noticeable on wide angles especially as they're cron and elmarit.

 

What are the other lenses which are in focus if 35/2 is not?

 

/markku

[Kent10D]

I'm curious about this.

 

Is there any info anywhere about how individual lenses are adjusted for optimum focus? I assume that there must be some way of adjusting the position of the rangefinder coupling cam on the lens, and I also assume it's a precision task not to be undertaken by mere mortals, but I'd be very interested in knowing how it's done.

 

Cheers,

 

Kent.

[wattsy]

Don't assume that if you send it back to Solms it will come back focussing correctly. Solms had both my 50 ASPH and M8 in for focus 'tuning' earlier this year but returned the combination to me with a reduced but still noticeable back focus problem. I've since acquired another M8 and the 50 back focusses exactly the same on that one so I'm quite sure it's the lens. It's very annoying because I can only reliably use the lens stopped down three or four stops and £1500 or so seems a lot of money for what is currently (for me) a '50/F4'. I also had similar problems with a 35 ASPH 'lux (back focus and significant focus shift) which Solms were unable to do anything worthwhile about. I ended up selling that lens and replacing it with a 'cron (which focusses absolutely fine). I'd do the same with the 50 but I know from experience that the current 50 'cron is too susceptible to veiling flare for my liking (I shoot into the evening sun a lot).

[charlesphoto99]

Keep in mindhere are two different problems at work here.

 

One being the plane of focus off either by rangefinder or lens maladjustment.

 

Two is the lens plane of focus shifting back when one stops down the lens. So lens is in perfect focus wide open but is thrown out of focus as one stops down, esp around f4 (before massive depth of field can kick in). This has been esp prominent with my 35mm Lux Asph (a known issue); somewhat with my 50mm Lux pre-asph (despite being adjusted by DAG for problem #1), not a problem with my other lenses. Frustrating and I think there's very little Leica can do about it. I adjusted my rangefinder focus forward just a bit to compensate for the problem. So I'm not as tack sharp wide open but focus is a bit better stopped down. Not really a problem in real world as when using wide open it's generally low light and hard to perfectly nail the focus anyway.

 

BTW: the allen key thing may be working for many of you, but with lots of testing I find that without adjustment of the near/far (washer underneath screw at start of the arm) that mid distance focus can be thrown off. Not as easily noticeable as close or infinity, but can be a problem. So be sure to test your focus at near, far and middle distances when adjusting the rangefinder.

[delander †]

Hi to everyone,

 

I am a recent convert to Leica and intrigued and a little concerned about the focusing issues.

 

Surely Leica must have a test rig at the factory which is used to correctly adjust every M8 body for focus, virtually the last thing done to the camera. The technican must do this adjustment until the body falls within spec. How does he know, by experience or is it actually measured?

 

Similarly there must be a test rig for lenses to check focus and this test rig must be accurate in relation to the body test rig.

 

The standard on both the body and lens test rigs must be set so that the worst performance combination is insignificant for the user.

 

The card that comes with the camera/lens is barcoded and signed and states that 'This Leica product was meticulously examined by experienced professionals at several stages of production'.

 

The word 'meticulous' means careful, punctilious, scrupulous, precise!

 

Does the Leica Test Certificate mean something or what? If it does then Leica surely needs to tighten up on its tolerances.

 

I have an M8 and a number of new lenses although I have stayed away from Summilux lenses because of their expense. I have not done any real tests but often feel that with the Summicron 50mm at f2-f4 when used at short distance does back focus an inch or two.

 

Also what about Zeiss lenses? Does the problem exist with those lenses as well. How does Zeiss ensure its lenses focus properly on a Leica M8. Presumably it uses its own test rigs to check the lenses for focus but on what camera body, surely a Zeiss Ikon. Or is there an agreed standard between Leica and Zeiss?

 

More questions than answers I am afraid,

 

Jeff

[carstenw]

It appears that even the Leica test rig requires some experience to operate correctly. Leica has by necessity recently re-hired many people, as well as hired entirely new people, and these must all be trained. In the past, the error was certainly less than the perceptible in the large majority of cases, but the combination of the new hires, combined with the exceedingly exacting error thresholds which come with digital, appear to have overwhelmed the system for the time being. It will surely be brought under control with time, but I fear that we have to accept that at the moment, mistakes will be made, and equipment will have to be sent more than once, on occasion.

[atufte]

I hesitated as well as two of my lenses seemed to be OK and two far from it.

I've always been a bit curious person, so I had to try and see what happens. And especially if you remember how much you've turned the key and to which direction you could always go back to original setting:)

 

So I tried and the situation now is a lot better as my wide angles are still OK but 50 and 75 don't back focus anymore.

 

It is 100% sure that the focus plane has moved on every lens but lucky me it isn't noticeable on wide angles especially as they're cron and elmarit.

 

What are the other lenses which are in focus if 35/2 is not?

 

/markku

 

My other lenses which works perfectly is:

 

28/Asph, 50/2 and 90/2...no problems what so ever...

[atanabe]

The term "Back focus" is an abused term on this forum. In truth, a "Back focus" is a mis-aligned lens either through internal elements being out of specification or a flange to film plane being out of tolerance. The term that should be used is "rangefinder needs adjustment". The M series of cameras has a mechanical coupling between the armature within the camera and the back rim of the focusing helicoid of the lens. As the focusing helicoid is turned from near to far the armature is moved in and out. Which in turn move the semi silvered patches left and right.

 

A true test of "Back focus" would involve setting the camera on a tripod the lens focused on an object past the infinity distance scale (greater than 200 feet). If the lens flange to film (sensor) distance is off you will see it here as a fuzzy image. Keep in mind atmospheric dust and the heat wave distortion when choosing your subject. If the obect is in focus then your flange to film distance is correct. Each lens that leaves the factory is adjusted for the flange to film distance using an optical test chart. If it is out of tolerance, shims are inserted to compensate for the distance. When you send your lens in for the 6 bit coding it is also checked for the flange to film distance. This is critical as it determines the exact point where the light rays are focused on the film plane. It will also determine how deep the focusing helicoid is depressing the armature. With this in mind an object the thickness of a hair on the helicoid could set off focus.

 

The armature for the rangefinder is set for an average lens, to adjust the armature precisely would require that each lens be sent in with the camera for an adjustment. So if your lens has passed the infinity test, now choose a high contrast mid distance target. Focus using the rangefinder, use the magnifier if you have one, then take three shots. The first with the rangefinder perfectly focused, second with a slight twist of the lens closer and finally a slight twist farther. If the closer or farther image is better than the rf focused one then the rangefinder needs adjustment. Send it to Leica Service and have them do the adjustment, if needed send the offending lens as well.

 

One reason that this has not come up in the past is with film, we did not use a loupe greater than 8x to look at our chromes and we blamed ourselves for not getting the focus right the first time. With digital we chimp the image after we shoot it and look at it at 100x magnification.