Not Your Everyday Banana

by Bart Arondson

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I'm just starting out with DLSR photography - I recently purchased a Sony A230 with the kit lens (18mm - 55mm). I know that the lens mount is compatible with Minolta lenses. These lenses were originally designed for film SLR cameras, and I'm wondering what impact that will have when I go to use them with my camera. Some websites advertise lenses for a Minolta mount that have the ominous warning NOT FOR DIGITAL SLRs.

What am I getting myself into when I buy older film SLR lenses? I have heard that the effective length of the lens changes due to the different sizes of the image sensors, but how can I calculate this? Are any other lens specifications, like aperature size, that are changed? Will autofocus still work? Will my camera be able to read the lens? What would happen if I bought the lens that is linked above - would it really not work with my camera or give horrible results?

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As noted, this is PROBABLY mostly about Minolta MF lenses not being directly compatible with the A Mount AF system. "One would hope" ALL A-mount compatible lenses would work with any film or digital A Mount camera. In a very few cases, the sweep of the camera mirror may interfere with the lens. This is exceedingly unusual. As I recall (perhaps incorrectly) some specialist teleconverters that will not work in some cases. Having written this it hardly sounds credible, but that's what the brain offers at present :-). || What's wrong with 'Tony' - head injury? email address on my profile –  Russell McMahon Apr 10 '13 at 3:29
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2 Answers 2

up vote 9 down vote accepted

Minolta, like Canon, changed their mount when they moved to AF in the 1980s. Only Minolta AF lenses can be used on Sony's Alpha mount.

The field of view will be cropped due to the fact that the sensor in your camera is smaller than the imaging size of film. So a 50mm lens will have the field of view of a 75mm lens, as the crop factor is 1.5.

Here's a good answer about crop factor in DSLRs

Aperture is unchanged. AF should work fine!

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I've successfully used some late-90s Minolta SLR lenses with an Alpha 100, with no problems whatsoever. They are exactly the same as the newer lenses. I use a Minolta flash, too. –  TREE Feb 6 '11 at 0:11
    
Minolta xi lenses will lose their autozoom functionality (a neat trick where you could link zoom to autofocus and maintain subject size automatically -- it was great for runway fashion). Third-party lenses, though, are a coin toss; if the maker reverse-engineered the Minolta AF/AE interface right, they'll work, but there's no guarantee. –  user2719 Feb 6 '11 at 6:11
    
Thanks for your response. Aperture not changing took a bit of thinking, but I got it now. –  W5VO Feb 7 '11 at 5:19
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On thing is crop factor. This is not really a problem. One gets just more zoom and less wideangel.

The real problem is flare from the sensor. Lenses made for digital SLRs have a coating that reduces flare; the older film-lenses do not have this - it was not needed when using film.

But the lens can/will work and most likely take good images.

Regards Sigersted

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So does this lack of coating to prevent sensor flares a "deal-breaker" on older lenses, or is it something I'll only notice under unusual circumstances? –  W5VO Feb 7 '11 at 5:15
    
@W5VO - "older" in this context means stuff from the '60s. Sophisticated multicoating has been a standard feature of lenses claiming anything like quality for a very long time. And flare was every bit as big a problem with film as it is with digital. All Sony and Minolta AF lenses are multicoated, as are all of the Sigma and Tamron lenses for the Sony/Minolta AF mount. Really cheap off-brand lenses may not be, not because they are old, but because they're cheap. –  user2719 Feb 8 '11 at 17:15
    
You can't see whether or not all lens elements are coated, but you can tell whether the front and back elements are coated on the outside at least. Look for a sort of rainbow in light reflected from the elements -- if you don't see a sort of rainbow sheen on the lens (front and back) of a used major-brand lens, it's because somebody "cleaned" off the coating. If you don't see it on an off-brand lens, new or used, it's probably because it isn't multicoated (or coated at all). –  user2719 Feb 8 '11 at 17:18
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