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Author Topic: Infinity focusing when using legacy lenses on NEX  (Read 1581 times)
waterden
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« on: January 11, 2012, 08:56:07 AM »
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My first post on this forum although I have "tuned in" to LL many times over the years.

Firstly, and this is well overdue, a big thank you Michael for providing such an interesting and balanced site. I enjoy reading your real-world, common-sense articles and I though the recent ones on the NEX-7 were exemplary.

I became interested in the NEX system as a small form factor vehicle which would enable me to use once more my old Minolta manual lenses and also some Voigtlander VM and Leica M ones. I have used these successfully on the NEX-5 but there has been obvious lens cast from the wider (28 down) VM lenses which, as noted by Michael, is easily if somewhat tediously corrected in Cornerfix. I have not noticed lens cast with Minolta lenses, even on the widest 24/2.8 one I use, but this may be subject related (obfuscating the cast) as I have only used it on a couple of occasions.

There is another issue I have noted after trying out my new NEX-7 with VM and ZM lenses. They focus beyond infinity. I rarely focus to infinity, and when I do it is usually at apertures around F8, and it was only when testing this camera with a ZM 50 C-Sonnar (great lens) that this became obvious. For objects more than 400 metres away the adjustment needed is minor but I have not yet found a distance far enough away to allow the lens to be set at infinity and focus correctly when near to wide open. I have checked the effect with other equivalent lenses and several top notch adapters and in all case the effect is the same or similar. Fortunately, the MF Assist allows accurate focusing but it does need to be used, even for very long shots. It may be that this is a by-product of using adapters where, even with tight manufacturing tolerance, it is important to allow for perhaps lesser tolerances on lenses and avoid the risk of under-focusing at infinity.

So the lesson appears to be when focusing manually with legacy lenses that the lens distance markings and infinity stop are not accurate and will not, moreover, be particularly helpful for DOF estimation unless you remember that, as Einstein might have said, infinity is not where you think it is.
« Last Edit: January 12, 2012, 09:39:01 AM by waterden » Logged
wildlightphoto
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« Reply #1 on: January 11, 2012, 09:20:24 AM »
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So the lesson appears to be when focusing manually with legacy lenses that the lens distance markings and infinity stop are not accurate and will not, moreover, be particularly helpful for DOF estimation unless you remember that, as Einstein might have said, infinity is not where you think it is.

I'd say the lesson is to use adapters that are the correct thickness.
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waterden
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« Reply #2 on: January 11, 2012, 09:25:36 AM »
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Well the Voigtlander M to E adapter is supposed to be as good as or better than the Novoflex while the Metabones M adapter is recommended by Photozone. As for the LA-EA1 adapter, it is made by Sony so presumably must be correct thickness for the job.
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