Quote:
Originally Posted by Maltesekilli
I own a Sony A100, and recently bought a Minolta MD 28mm f/2.8 lens for it.
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MD/MC lenses on the Alpha mount are problematic. It's the
Minolta AF-mount lenses that will mount directly to a Sony Alpha. The older MD/MC mount was shallower from the image plane to the back element of the lens--so can't use a simple metal ring to adapt
and maintain inifinity focus. So you have to get an
adapter with a glass element in it, and just like a teleconverter, that will rob you of image quality. Still might be worth it, though.
Because the lens can't talk to the body, though, you will lose the ability to shoot in any modes other than full manual and aperture-priority, autofocus, and possibly metering. That's what you give up when you go for the vintage glass bargains.
Quote:
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Since the lens bought is M49 and my SLR is M55, I needed a step-down ring .. am I right??
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You got a little terminology confusion here. The M49/M55 you're talking about is the
filter size--it's the diameter of the front filter thread in millimeters. It doesn't have anything to do with the back end of the lens. A step-up/step-down ring is for adapting a differently-sized
filter to a lens.
It's
easy to get confused about this, because back in the day, the really old mount systems were also just threaded holes of a certain diameter. And two of these mount systems are called M42 (aka "screw-mount Pentax") and M39 (rangefinder, aka LTM, aka Leica Thread Mount aka Leica screwmount).
BTW, you
can adapt M42 lenses to the Minolta AF/Alpha mount with
a simple metal ring, which won't rob you of image quality. A lot of folks are snapping up the M42-mount Takumars and Carl Zeiss Jenas for adapting (just check they're not Pentax K-mount or Contax/Yashica mount, respectively).