28mm Summicron on micro four thirds? corner softness?

[jankap]

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No, Jan. The lens is designed for a particular distance, flange to sensor. The adapter simply adds the missing extension to allow the lens to focus to infinity. The adapter isn't an "extension ring."

 

Extension tubes are used to focus closer than the lens' helicoid allows; they are not "in the optical path," but locate the lens further from the sensor. The increased distance means the light travels further, and its intensity is decreased. Same thing happens when you focus a macro from infinity to 1:2: There is a reduction of the amount of light transmitted.

 

That's completely different from the use of the adapter in question, because the adapter is a tube that returns the lens to its infinity focus capability.

 

Of course. I do not know how many extension the adaptor has to deliver.

The whole diskussion does not explain, why a not-wideangle focal length of 56 mm (equivalent 28 mm on 4/3) should cause softness. Is there a comparable 28 mm Not-Leica with better results as the Summicron?

We have no means to measure the amount of softness in a neutral way, I suppose?

Jan

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[ho_co]

Jan--

Wideangle lenses designed for reflex cameras don't show the problem. If you want to get good quality from Micro FourThirds with short focal lengths, use R lenses instead of M.

 

'Symmetrical' lenses are designed with the steeper ray angles that cause the difficulty. Retrofocal lenses produce rays that strike the sensor closer to the vertical.

 

One reason Leica wide-angles have traditionally been so good is that the designers didn't have to design them to get out of the way of a mirror. Adding that constraint is one reason that most wide-angles for reflex cameras don't perform particularly well.

 

But now we're talking about sensors, for which the M lenses until recently weren't designed.