SLT-A57 or lens Wide angle focusing (issue?)

Generally speaking AF has problems with wider angles of view, some camera models more than others.How wide the problems start depends on the camera model.The best focus will always come from the central AF sensor, so I hope that's the one you were using in your tests.

My own rule of thumb is to start checking the AF at around 20mm. The smaller the focal length the worse the problems. By 18mm my Sony A350 and A550 were right off, seriously front focusing. Whereas my A77 seems to manage good AF pretty well down to at least 14mm.

Which is why focusing problems are so often reported for wide angle lenses. AF isn't perfect. That's why the most expensive models with the latest best AF also have the most sophisticated methods for adjusting AF and for doing manual focus.

So I suspect there's nothing wrong with your camera. You're just discovering one of its inherent limitations.

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Chris Malcolm