Can Minolta A-mount lenses focus to infinity on a Canon EF camera with an adapter?
Asked 10/8/2015
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I tried using a Minolta/Sony A-mount lens on my Canon 600D with an A-mount-to-Canon EF adapter. Close subjects can be focused reasonably well, but distant subjects and infinity are always soft, even on a tripod with a remote release. Is this due to the flange/register distance between Minolta A-mount and Canon EF, and can infinity focus work at all with this kind of adapter?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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It's definitely worth reading Can I use lens brand X on interchangeable lens camera brand Y? and the answers to Why I can't find an A-mount to Canon EF Adapter?, but the issue here is that the registration distances for the Canon EF mount (44.0 mm) and Minolta A mount (44.5 mm) are very close - just 0.5 mm apart. This means that for an adapter to allow infinity focus, it would need to be just 0.5 mm thick and that's not enough to contain all the physical bits needed to get the lens mounted - therefore you do lose infinity focus when trying to mount an A mount lens onto an EF mount, unless the adapter has a glass element in it.
Originally by user11371. Source · Licensed CC BY-SA 4.0
user11371
10y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — this is a register/flange distance issue. Canon EF has a 44.0 mm flange distance, while Minolta/Sony A-mount is 44.5 mm. Because the mounts are only 0.5 mm apart, a simple mechanical adapter would need to be about 0.5 mm thick to preserve infinity focus, which is generally too thin to physically implement the mount structure.
As a result, a plain A-mount-to-EF adapter usually will not allow infinity focus, so distant subjects stay soft no matter how carefully you focus. Infinity focus is only possible if the adapter includes an optical element, but that adds glass and can reduce image quality.
So your results are consistent with the adapter design rather than a problem with your technique or tripod stability.
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