a to nex lens adapter

Started Jun 30, 2010 | Discussions thread
Brian_Smith
Senior MemberPosts: 1,385
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Re: a to nex lens adapter
In reply to KEITH-C, Jul 5, 2010

KEITH-C wrote:

It's my guess that contrast detection is performed at the pixel level or across a small group of pixels & that any camera shake can confuse the adjustment algorithm especially in low light.
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Keith-C

Keith,

Contrast AF is based on the principle that an accurately focused image has the highest contrast among all images of the same scene. The lens racks back and forth until it finds the focus point that has the highest contrast. This works best in bright light focusing on sharply defined lines like black and white stripes. On the other hand, low light and a low contrast scene are probably the worst situation situation.

The E-mount lenses are optimized for the NEX cameras. In most situations, they focus quite quickly - much faster than Olympus PEN. Screw drive lenses are a different story. It's kind of like trying to use a hand drill to turn a cement mixer. While it might be possible, it's not the best solution.

I've used the Alpha-NEX Camera Mount Adapter with screw drive lenses including the 135/1.8 and 100 macro. You can zoom in on a focus point anywhere in the image (not just the center) and view it at 10x for critical focus. It works just fine manual focus, but I doubt it would be your choice for shooting sports action. Then again, an a900 and 300/2.8 probably wouldn't be my choice for a walk-around body. Different tools for different uses...

Brian Smith
http://www.briansmith.com
http://www.briansmith.com/blog

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