M8 backfocus

[johnkuo]

My 3 day old M8 seems to exhibit backfocus (about 1 cm or less) near the closest distance. I have tested with 50 noct, 50/1.4ASPH and 75/2.0ASPH. I need to do more testing, but right now I can sort of compensate by adjusting the focus point just a tad closer. Has anyone encountered this on their M8? I would like to have it adjusted at some point, but I imagine Leica NJ would be busy right now with other M8 issues. Any idea what the turn around time would be for such adjustment? Fortunately everything else is A-OK so far. I'm very pleased with the image quality, now if only the focus is spot on...

Thanks.

[KJB]

Originally Posted by johnkuo

My 3 day old M8 seems to exhibit backfocus (about 1 cm or less) near the closest distance. I have tested with 50 noct, 50/1.4ASPH and 75/2.0ASPH. I need to do more testing, but right now I can sort of compensate by adjusting the focus point just a tad closer. Has anyone encountered this on their M8? I would like to have it adjusted at some point, but I imagine Leica NJ would be busy right now with other M8 issues. Any idea what the turn around time would be for such adjustment? Fortunately everything else is A-OK so far. I'm very pleased with the image quality, now if only the focus is spot on...

Thanks.

21ZM and 90 Lanthar focus is right on
Faster glass:
Noctilux frontfocus
CV 28 Ultron backfocus
Have tested them at close and long distances and get the same issues with the Nocti and Ultron. I've learned to compensate also but I would probably get a better % in focus after sending to Leica for calibration.

[erl]

I sent my Noct back to Solms with my M8 for its 'fix'. I complained that the Noct was back focussing at close range. I am waiting for them to return, hopefully in a few weeks.

Cheers,
Erl

[neila]

Just for those that don't understand (i.e. me) what is 'back focussing'?

I'm about to get my M8, so it would be useful to know.

Thanks

N

[ericc]

Originally Posted by neila

Just for those that don't understand (i.e. me) what is 'back focussing'?

I'm about to get my M8, so it would be useful to know.

Thanks

N

Put simply,

You set up a rule at an angle of 45 degrees leaning away from you.
You then take the lens you are testing, set it to its closest focussing distance and by moving the camera forwards or backwards focus on say the 6 inch mark on the rule.
If the 5 inch mark is sharper then the lens / body combination is showing front focus and if the 7 inch mark is sharper then the lens / body combination is showing back focus.
At least that is the way i understand it. :-)

Regards
Eric

[tom0511]

My Noctilux frontfocuses, my 50/1.4asph backfocuses,
28,35 once frontfocused on my rd1 and I had sent them in for calibration, which helped.
My 75/1.4 and 90/2.8 are spot on.
If all your lenses show the same tendency to front focus I would gues that it is the camera and not the lenses?

[johnkuo]

I have used all these lenses on my three film M bodies, and didn't have any issues. But again with the delay of film processing and scanning, it may not be as obvious as the M8. I should do some more testing with the film bodies as well.

[tom0511]

Originally Posted by johnkuo

I have used all these lenses on my three film M bodies, and didn't have any issues. But again with the delay of film processing and scanning, it may not be as obvious as the M8. I should do some more testing with the film bodies as well.

some people say, that the sharp-unsharp-transition is more harsh with sensors. Films have a certain thicknes vs the sensor, as I understand.
So slight missfocus might show more clearly when shooting digital.

[lct]

Originally Posted by tom0511

...slight missfocus might show more clearly when shooting digital.

Agree, digital is less forgiving as far as focus, now using a 1.25x magnifier with fast 50's and up might help at full aperture given the rather low magnification of the M8 viewfinder.

[fredbonhomme]

I also have 2 to 3 cm of back focus with my M8 and 35/2 or 50/2,8

[khanosu]

I recommend using Tim Jackson’s templates for back focus testing; you simply print out the template and perform the test. You can download the templates and very clear instructions from here:

http://www.focustestchart.com/focus21.pdf

Material relevant to back focusing starts on page 13.

Instructions for using the templates: Page 13
Interpreting your results: 15
Actual template: Page 18

Furrukh

[johnkuo]

Furrukh, thanks for the link to the template. I printed on regular letter size paper, and find it too small to focus on consistently. After several shots, it does seem to confirm my earlier assessment that it backfocuses by 1cm. At some point I will send it for adjustment, but it's too much fun to use to be parted with for now.

[ho_co]

Originally Posted by lct

Agree, digital is less forgiving as far as focus....

Might be interesting for someone to try the focus test with the same lens and a film Leica.

That is, perform the focus test procedure Prof Khan mentions in post #11 on both one of your film Leicas and the M8. (Or just do the ruler test as Eric suggested in post #5.)

Use the same setup for both, just for consistency's sake--same lens, same distance etc. (The test obviously requires the cameras to be in 'portrait' instead of 'landscape' position as recommended for testing AF cameras.)

It may be that our lenses have been slightly off for decades and we simply didn't notice it with film.

Or it may be that our eyesight is getting worse and the reduced magnification of the M8 doesn't help.

Or it may be that a surprising number of M8's are exhibiting backfocus.

Isn't it interesting that the author of the test template feels that a deviation of 1 cm is fine for an AF camera, but for our Leica dollars we see that same discrepancy as a problem? Don't misunderstand: I agree, the focus should be exact. We expect sharp pictures from our Leicas; with another brand we wouldn't likely be so demanding either!

--HC

[neila]

Thanks Ericc - I wasn't sure.

If a camera is exhibiting either front or back focus I assume it can be adjusted?

[johnkuo]

With fast glass like the noctilux, that 1cm really makes a difference. I found it helpful that the M8 allows 100% view on LCD to check focus.

[ericc]

Originally Posted by neila

Thanks Ericc - I wasn't sure.

If a camera is exhibiting either front or back focus I assume it can be adjusted?

No problem.

If all of your lenses exhibit the same symptom then the camera body needs to be adjusted, however, if it is only certain lenses, then I have heard of lenses being adjusted to correct focus problems.

Cheers
Eric

[erl]

Originally Posted by ho_co

Might be interesting for someone to try the focus test with the same lens and a film Leica.

--HC

Howard, I intend doing just that when my M8 + Noct return from Solms.

In a manner of speaking, I have already done it in that I have never had a problem in 3 years with the Noct on film cameras (except for 'user error!'), but immediately noticed back focussing with the M8. My dealer and two of his staff had the same problem when I returned it. It will be very interesting to see what changes may be made by the Solms Knomes.

Cheers,
Erl

[drjon]

Originally Posted by erl

Howard, I intend doing just that when my M8 + Noct return from Solms.

In a manner of speaking, I have already done it in that I have never had a problem in 3 years with the Noct on film cameras (except for 'user error!'), but immediately noticed back focussing with the M8. My dealer and two of his staff had the same problem when I returned it. It will be very interesting to see what changes may be made by the Solms Knomes.

Cheers,
Erl

I have experienced this issue particularly with a new 35mm summilux which I have sent back to Leica for checking and re-calibration; the 35mm appeared to be severely back focusing at short distances, < 3m - OK at longer distances. I subsequently tested my other lenses using a tape measure flat on a surface: (24mm 2.8 (new); 50mm 1.4 pre-asph (ten years old), 75mm 2 (new), 90mm 4 (new)). They were fine except for the 50mm which may have slight back-focusing. I suspect the tendency to use the '100%' feature to view files exposes any inaccurate focusing and lack of calibration in the lenses more easily than was the case with film.

I checked the rangefinder and this appears fine; I also had a second M8 body for a while; the 35mm behaved identically on the other body so I do not believe that the M8 per se is the culprit. Defintely a case of digial and the new 10MB sensor being merciless with errors - either user-derived or equipment-related.

[jcbjr]

i've tested all my faster lenses (nocti, 75m 1.4, 50mm 1.4, 35mm 1.4) and find a consistent back focus problem. i've dealt with it so far by just making a slight adjustment manually when shooting, but will be having solms adjust what i assume is a camera problem, not a lens problem, when it's sent back for other hardware adjustment. just trying to decide when i can live without it for a month!

john

[khanosu]

Hi John (Kuo),

You are right, focusing on the template is a bit of a hassle; I put a vertical mark on the text (see attached picture) to assist me in focusing. This is the result from my 50mm Summicron wide open. I think that this result is acceptable since the focus point is within the depth of field albeit at the lower edge. My 90mm Summicron Asp also shows exactly the same behavior. Have not tested my 28mm Summicron yet.

The test was done on a tripod and timer was used to prevent any shake.

Furrukh