Medium format lens to the APS-C DSLR? Good or bad idea?

[robgr85]

I've started similar topic at Strobist.com group, wonder what are Your thoughts about my idea:

I am wondering about buying manual medium format primes to my EOS400D. There are mounts with AF cheating chips (AF confirmation) giving me the ability to connect medium format lenses to my camera. I am not worried about manual aperture setting and focusing. I am using now some M42 mount type lenses, and know how to cope with "full manual mode".

Just wonder about the image quality. What about image optical resolution (MTF)? Will it be better than with normal APS-C type lens? What about chromatic aberration and other distortions? I'm considering getting some Mamiya 645 sekor C lenses. Which ones? I would be pretty interested now in 80mm f4 macro and 210 f4 prime.

But... is it worth it? What about the image quality of Mamiya/Hasselblad prime lenses connected to aps-c body? My first thoughts when hearing 'mamiya' were allways associated with 'quality'. But how about connection canon-mamiya?

Or maybe the advantage of medium format photography is only in its sensor/film size, and the lenses does not need to be opticaly better than the ones dedicated to 35mm cameras?

I googled the topic, but it is very hard to find any samples Does anyone from here tried it? Can You post any samples? Did You performed any optical tests in similar setup?

direct link to the topic on flickr:
http://flickr.com/groups/strobist/di...7607540066435/

Any comments here on POTN apreciated.

Robert

[Wilt]

The larger the format for which a lens is designed, the lower the lines/per millimeter rating achieved by the lens. This is because of the need to cover a larger image circle, so achieving high rating in lines/mm is more difficult and expensive. Microfilm lenses offer super high resolution but they only need to deliver it to tiny microfiche sized images. You are right that the lenses for medium format do not need to be higher resolution than 135 format lenses; but they do not trail far behind, for the higher quality lenses.

[robgr85]

I do not know if I correclty understand You: You do claim that generally medium format lenses resolution is lower than small sensor ones.

Will there be any difference in image quality if I would manage to cover the APS-C sensor (lets say by bringing the lens closer to the sensor) with the entire picture generated from 645 format lens (is it technically possible to achieve that?)?


Cheers,
Robert

[Wilt]

Originally Posted by robgr85

I do not know if I correclty understand You: You do claim that generally medium format lenses resolution is lower than small sensor ones.

Will there be any difference in image quality if I would manage to cover the APS-C sensor (lets say by bringing the lens closer to the sensor) with the entire picture generated from 645 format lens (is it technically possible to achieve that?)?


Cheers,
Robert

Generally, Yes, the expectation is lower lens resolution. Reality may be wrong...an especially great medium format lens vs. an especially mediocre 35mm lens might have the medium format lens deliver more resolution, but that is an exception...usually at best you might assume equal resolution from the two lenses.

To answer your second question, while using a small medium format lens might provide greater resolution (I don't recall seeing this validated in tests) than a larger medium format lens (like 6x7), in theory what you say in the second paragraph is better.

[robgr85]

Thank You for Your explanation.

Cheers,
Robert

[DrPablo]

Originally Posted by robgr85

Will there be any difference in image quality if I would manage to cover the APS-C sensor (lets say by bringing the lens closer to the sensor) with the entire picture generated from 645 format lens (is it technically possible to achieve that?)?

A 645 lens will easily cover APS-C. There WILL be a difference in image quality, though. Imagine taking a 645 camera, taking a picture, enlarging it to a 24x36 inch poster. Now take an APS-C sized crop out of it and enlarge it to 24x35 inches. You'll have had to enlarge the APS-C image 3 times as much to get to the same output, which means that the detail density (aka resolution) will be 3 times lower.

Originally Posted by Wilt

The larger the format for which a lens is designed, the lower the lines/per millimeter rating achieved by the lens. This is because of the need to cover a larger image circle, so achieving high rating in lines/mm is more difficult and expensive.

And it's not necessary, because larger formats are enlarged less, and therefore don't demand so much on-film resolution.

That said, the Mamiya rangefinder lenses for 6x6 and 6x7 are as sharp as almost any 35mm lens out there, they consistently get 80-100 lp/mm. The Hasselblad-Zeiss lenses get 80 lp/mm, as do the Rollei-Schneider lenses.

But I don't see much of a point in adapting MF lenses for small format unless you're using it as a tilt-shift lens with an adapter.

[robgr85]

Tilt - shift is the primary project in which I want to use my Medium Format lens, but I wonder If there could be any other good usage field for that lens...

Cheers,
Robert

[DrPablo]

If you're interested in a tilt-shift, then I'd get a tilt-shift. The adapters for MF lenses are expensive unto themselves, and you have to be comfortable with manual aperture settings, etc. It's not a simple solution.

And since you mentioned it, I'd like to sell my Canon 24mm tilt-shift lens, which is in outstanding condition -- just need the funds for other things. So let me know if that interests you.