Sigma C 65 mm f/2 DG DN – first impressions - Autofocus and several words about optical properties

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Sigma C 65 mm f/2 DG DN – first impressions

1 December 2020

Maciej Latałło

3. Autofocus and several words about optical properties

The autofocus of the Sigma C 2/65 joined with the Sony A7R II camera is completely noiseless. Its speed we found moderate – running through the whole distance range and confirming the focus takes about 0.8-0.9 of a second. No matter from what end of the range you start the speed remains the same. Still, there were situations when focus was confirmed very far from the proper position; only the next pressing of the shutter made it change its position to the proper one.

Of course it's worth noticing that the performance of the autofocus of any pre-production model might differ greatly from what you will experience with the final version of the lens so we are very cautious with our assessment. It's better to abstain from any biding conclusions and wait for the proper test.

A7R II, f/2.0

Sigma C 65 mm f/2 DG DN – first impressions - Autofocus and several words about optical properties

Above you see a photo of our autofocus testing chart that shows not only the accuracy of the mechanism but also allows you to get a preliminary idea concerning the optics. First of all, longitudinal chromatic aberration doesn't seem to be corrected very well. The influence of this aberration is, fortunately, not very distinct but still it is far from perfect.

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When it comes to sharpness at the minmum focusing distance the situation is better than that of the 2/35 model but not as favourable as in the case of the Sigma 2.8/105 Macro. Once again outdoor sample shots show that sharpness at the maximum relative aperture is good so a possible weakening of its quality might be visible only at closer distances. Of course you should treat our remarks here very loosely, we will get to know the real situation only when we test final specimens, with a proper measurement of resolution for three different distances from the photographed object.

At the end we should say something about vignetting. Or preliminary assessment shows that there are much less problems in this area than in the case of the 2/35 model, presented at the same time. For the 65 mm Sigma brightness loss in frame corners shouldn't exceed 2 EV and it is a sensible result, especially if you take into account physical dimensions of the lens and the mount it was designed for.