Sigma 120-300 mm f/2.8 APO EX DG OS HSM review - Autofocus

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Sigma 120-300 mm f/2.8 APO EX DG OS HSM

2 August 2012

Arkadiusz Olech

10. Autofocus

The tested lens is equipped with an HSM motor so the focusing mechanism’s work is by and large noiseless. Still the autofocus can be hardly called fast. In typical lighting conditions running through the whole scale takes about 1-1.2 seconds and when it is darker it might take even longer. Taking it into account it’s a pity the producer didn’t include an autofocus limiter. Rival 2.8/300 constructions feature it and it seems it would come in handy in the case the tested Sigma as well.

On the other hand we can say only very positive things about the accuracy of the focusing mechanism. We had an opportunity to try the Sigma attached to the Nikon D3x in the field, while photographing the birds. Usually I take such photos using the Canon 50D and the EF 100-400 mm f/4.5-5.6L IS USM and I must admit the Sigma, even with the converter, fared a bit better than the Canon set. The number of good shots, focused exactly where I wanted, was noticeably higher. Of course you can start wondering whether the professional D3x camera, used in the test, didn’t influence such a good result more than the lens itself. It is undoubtedly a pertinent and legitimate question but I just wanted to provide a reference point for the Readers of this review.

When it comes to the studio test, the Sigma fared well too. The number of misses didn’t exceed the level of 4% which should be considered a fully satisfactory result.

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We didn’t notice any front or back focus tendencies when the tested lens cooperated with the Nikon D200 – the device worked properly. After changing the body to the D3x we perceived a slight front focus but it was noticeable only in the photos of objects situated very close by, with the shallowest depth of field; the front focus was also very easy to correct using the micro regulation available in the menu of the camera body. It is also worth adding that the level of that front focus was similar at all short focal lengths so the micro adjustment could correct it well without the necessity of taking the lens and the body in for a service.