How to determine backfocus on 35lux

[rycm]

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I read a lot of the backfocus issue for the 35lux on the M8.

I have these too, however, I use my 28 elmarit more often on the body. Appreciate if someone can let me know the best way to determine if I do have a back focus issue.

And if I do, is the adjustment made on the body or the lens. Thanks.

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[luigi bertolotti]

It's not a difficult test: you need a focus chart that can be found on the net, ready to print; then you must use it properly, with camera on tripod and lens axis angled 45° to the sheet of the focus chart: focus at the reference on the focus chart, at a distance of 1 - 2 meters, then make a series of shots at 1,4/2/2,8/4/5,6... (last stops like 16 11 are unuseful for such test), keeping the focus strictly unchanged : if your lens has focus shift, you will notice clearly that the best-focused point (which can or CANNOT coincide with the reference you focused on) is not always the same, i.e., it "shifts" while diaphragm is closed. The possible "adjustement" is anyway a compromise, and is a delicate tuning lens+body that must be done at a lab (probably, better at the factory).

 

Of course, the test can be more complete as one likes to do... I spoke of ONE series of shots at a distance of 1-2 meters... of course, one can do many of them... at 70 cm, 1 mt, 1,5 mt, 2mt etc... , with a 35 mm lens, is nonsense to make a test, say, at 5 /6 meters... the small details of the focus chart become unreadable while enlarging the image.

[jaapv]

You only need to start testing if you notice consistent misfocus on your photographs - and even then it is doubtful if you should attempt to diagnose the problem yourself - get the camera to a qualified repairman. As for DIY focus adjustments - for lenses forget about it - you need shims, adjustment targets, a collimator and expertise. For the camera - you can do one or two simple things yourself. The vertical adjustment is easy - although you need a special tool. Horizontal (distance) is a bit of a lucky dip. If it is the infinity adjustment only that is off, you can adjust it with a 2 mm Allen wrench. It is OK as an emergency attempt on the road, but you need to be lucky. Often it will get infinity right and all other distances off. The other two adjustments, again, are better left to the expert.

[luigi bertolotti]

Ugh... sorry... you asked about backfocus and I answered about focus shift...