Sigma 17-50 2.8 focus issues?

Started Mar 19, 2012 | Discussions thread
OP doak Regular Member • Posts: 112
Re: Sigma 17-50 2.8 focus issues?

Thanks for your points.

awaldram wrote:

Guessing these are center crops.

Yes they are.

What makes you think the camera will focus on the center rather than the higher contrast bold writing ??

Because my Pentax 18-135 DC focused on the 1700 text every time from the same distance and angle. All the shots i made had the center focus spot on the 1700 text.

Would the larger aperature of the 17-50 impact the focus results?

The sensor will cover quite a wide area within the center of the frame (about 6% from memory) and lock onto the highest phase variance within that frame.

It appears with your shot the camera has behaved spot on and achieved its design performance criteria.

Try using a proper focus target where the intended focal point is not ambiguous.

I'll try using the chart found here and post updated results.

I did shoot other objects in a well lit area (some with isolated areas of high contrast) and found the focus performance of the 17-50 not even close to the Pentax 18-135 DC nor my Tamron 90mm macro.

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