Sigma 50-150 mm f/2.8 APO EX DC OS HSM review - Autofocus

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Sigma 50-150 mm f/2.8 APO EX DC OS HSM

13 February 2013

Arkadiusz Olech

10. Autofocus

The tested Sigma is equipped with an ultrasonic autofocus motor called the Hyper Sonic Motor (HSM) so the work of the focusing mechanism is very quiet. When it comes to its speed, though, the situation is not so rosy anymore. Running through the whole distance range takes the lens about 1.2 seconds and that result doesn’t seem to depend on the conditions - anyway similar results we got with good lighting and in the shadow as well.

Still it’s worth mentioning here that most of full frame 70-200 mm lenses, and the Sigma 50-150 mm OS is supposed to be the equivalent of those, usually have minimum focus distance of 1.2-1.4 meters. The Sigma’s minimum focus distance amounts to 0.8 of a meter. It’s working range is wider and the challenge for the AF motor – greater. I am curious why there is no ‘Macro’ word in the name of this lens, by the way. The Sigma 70-200 mm f/2.8 EX APO DG HSM Macro, not produced anymore, focused from 1 meter after all and it got it in its name.

The Sigma 50–150 mm OS, while attached to the Canon 50D, provided good accuracy of the focusing mechanism - in studio conditions the number of misses reached 4%.

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We also didn’t have any problems with front or back focus tendency. The lens didn’t need any autofocus microregulation no matter what focal length you used – the photos below show it very well. Despite the fact that we took photos with the shallowest depth of field and from the smallest distance possible, both at 95 mm and at 150 mm the depth included the proper target so we can’t complain about any errors here.