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Lens review

Sigma 28 mm f/1.8 EX DG Aspherical Macro

2 April 2010
Szymon Starczewski

10. Autofocus

Sigmas without an HSM motor are known for its noisy focusing mechanism. The 1.8/28 model is not an exception to this rule. During focusing the autofocus works too long and definitely too noisy. What’s more it often misses. In the case of the Canon 20D, as much as 20% of the ISO chart pictures were so definitely out of focus that their MTF50 measurement was by more than 20% worse than the best possible resolution value.

On the Nikons D200 and D3x the accuracy was better but the noise and speed of the mechanism remained the same. On the D200 the number of misses reached 16% and only on the D3x we could see a more or less satisfactory performance because the number of misses achieved the level of 10%.

When it comes to the front or back focus tendency the news are not good. On the D200 we noticed a significant front focus and we could do nothing about it because that body doesn’t feature an AF calibration system.

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Sigma 28 mm f/1.8 EX DG Aspherical Macro - Autofocus

On the D3x originally we saw the same level of front focus but this time we could use the correction from the body level and the problem was swiftly solved.