M11 and 90mm f2.4

[jaechong]

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I just bought a 90mm Summarit and tested it on my M11. The lens is either front or back-focusing when focusing through the viewfinder. I tested various distances, and all gave me the same result. Focusing using the LCD screen with focus peaking is, on the other hand, very accurate. Can anyone tell me what the issue is? Thank you so much. 

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[Photoworks]

Send it in for calibration. 
my copy is very accurate

[nilsen]

Also, when you've gotten it calibrated, I recommend getting the 1.4x magnifier for the viewfinder. Focusing becomes a breeze

[jgeenen]

Can it be a calibration issue? Yes, that cannot be ruled out. On the other hand - very often the root cause is behind the camera.

I have a 1983 Summicron 90mm where I suspected focus calibration issues myself. As you experienced I found good focus in EVF but focus errors using OVF. Then I did the reverse testing - I mounted the camera on a tripod, focussed using EVF and checked the rangefinder patch alignment in the OVF. To my surprise, the patch alignment was good, no adjustment required. If your lens shows a signficant discrepancy, it might well be a calibration issue.

I then specifically trained myself focussing the 90mm lens. I always start at infinity (or larger distances) and dial clock-wise. I try to hit the focus on the first turn of the ring (I found the iterative approach "wiggling" with the focus ring to optimize patch alignment counterproductive). This has reduced my failure rate significantly. Am I able to nail focus with the 90mm lens at f/2 or f/2.8 every time? No, I am not and the 60Mpix M11 is not forgiving at all.

[fenykepesz]

vor 6 Stunden schrieb jgeenen:

Can it be a calibration issue? Yes, that cannot be ruled out. On the other hand - very often the root cause is behind the camera.

I have a 1983 Summicron 90mm where I suspected focus calibration issues myself. As you experienced I found good focus in EVF but focus errors using OVF. Then I did the reverse testing - I mounted the camera on a tripod, focussed using EVF and checked the rangefinder patch alignment in the OVF. To my surprise, the patch alignment was good, no adjustment required. If your lens shows a signficant discrepancy, it might well be a calibration issue.

I then specifically trained myself focussing the 90mm lens. I always start at infinity (or larger distances) and dial clock-wise. I try to hit the focus on the first turn of the ring (I found the iterative approach "wiggling" with the focus ring to optimize patch alignment counterproductive). This has reduced my failure rate significantly. Am I able to nail focus with the 90mm lens at f/2 or f/2.8 every time? No, I am not and the 60Mpix M11 is not forgiving at all.

with "calibration issue" do you mean now a problem with the camera body or with the lens ?

for checking more accurately back/front focusing issues with my M10-D + lens, i use some setup with a tripod and a metric ruler and take pics at various distances.

but then i realized that a very convenient way to quickly check RF focus issues is to take a photo of a target on your computer monitor (in my case a 110cm screen with 0.25mm pixel size), where - if taken from an angle and at a close distance, some 70cm - the moiré pattern with the monitor pixels is most distinct at the area of best focus, ideally around the target of your choice obviously.  once that not the case i begin to digg further to evaluate the calibration problem.

regarding the 60MP problem i feel nothing leads around IBIS - imagine taking photos at ISO:64 on a not-so-sunny day...