I've noticed an odd thing w/old Minolta/Rokkor legacy lenses....

[Mjollnir]

I currently shoot several of them with an adapter on a GH2, almost exclusively landscape and then almost exclusively at infinity because it's mostly in the eastern and western Sierra and Death Valley, so there are BIG distances and BIG vistas, etc.

I've noticed that the sharpest focus occurs juuuuuuuuust before twisting the focus ring as far as it can go towards infinity.  IOW, if I go to infinity and then dial it back just a wee bit, there is noticeably better, sharper imagery.  This happens with every one of the lenses I use, from a 50mm 1.4 to a 200mm 2.8 to a 135mm 2.0

Anyone have any idea why this might be?

[ErikKaffehr]

Hi,

Tolerances. If focus would be at exactly at infinity, half the lenses would not be able to achieve exact focus. So the infinity stop is set slightly beyond infinity.

Or, it could be possible that the adapter you have is a bit short, but it is probably better than the other way around, because in that case you would not be able to achieve exact focus at all.

Best regards
Erik

I currently shoot several of them with an adapter on a GH2, almost exclusively landscape and then almost exclusively at infinity because it's mostly in the eastern and western Sierra and Death Valley, so there are BIG distances and BIG vistas, etc.

I've noticed that the sharpest focus occurs juuuuuuuuust before twisting the focus ring as far as it can go towards infinity.  IOW, if I go to infinity and then dial it back just a wee bit, there is noticeably better, sharper imagery.  This happens with every one of the lenses I use, from a 50mm 1.4 to a 200mm 2.8 to a 135mm 2.0

Anyone have any idea why this might be?

[qwz]

Your adapter is a little bit short.

[Sussex Landscapes]

 your adapter is a little thin, with adjustment howevr it will be fine bang on infinity.

you need to read : http://www.davidclapp.co.uk/blog/view/setting-up-camera-adapters-tutorial

simon

[marcmccalmont]

I thought all slr lenses focus past infinity to account for extreme temperatures?
Marc

[mediumcool]

I thought all slr lenses focus past infinity to account for extreme temperatures?
Marc

Not in my experience; though I recall some long lenses perhaps with special glass elements with beyond-infinity focus. because of potential expansion of both the elements and the metal lens barrel.

[Rob C]

Not in my experience; though I recall some long lenses perhaps with special glass elements with beyond-infinity focus. because of potential expansion of both the elements and the metal lens barrel.

Yes, Nikon actually mentioned the focussing beyond infinity situation years and years ago in some literature supplied with, I think, my 4.5/300 IFED and the 500 mirror certainly does the same.

Expansion was the reason given for it.

Rob C

[Remo Nonaz]

I have a GH2 and adaptors for Pentax M42, Minolta, Konica and Nikon. They ALL focus past infinity. Don't assume you can twist the lens all the way to one end and be focused at infinity. This also throws off the distance scale a bit. For reasons I can't explain generally, and it varies by lens and adaptor, the correct focus distance mark is close to the IR focusing mark.