Sigma C 35 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 2/35 joined with the Sony A7R II camera is completely noiseless. Its speed we found quite sensible – running through the whole distance range and confirming the focus takes about 0.6-0.8 of a second. No matter from what end of the range you start the speed remains the same. What's more, we didn't notice any focus play or wavering – the autofocus always goes in the right direction and it doesn't miss.

Still, it's worth noticing that the performance of the autofocus of the pre-production model might differ greatly from what you will experience with the final version of the lens so we are very cautious here - it's better to abstain from any biding conclusions.

A7R II, f/2.0
Sigma C 35 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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A quite average sharpness near the middle of depth of field (so at 0 on our scale) is another issue. It might mean the lens performs a bit weaker at the minimum focusing distance. If you want to see a perfect image in this category, go to our latest test of the Sigma A 105 mm f/2.8 Macro. Once again, you have to remember two things.First, it is not exactly fair to compare this lens with a macro device because a macro lens is designed to perform the best at small distances, something which is definitely not true for the 2/35 model. Additionally, sample shots made by f/2.0 don't show anything disturbing so it seems the new lens fares quite well at greater distances. Of course only after a full test we will be able to know all details.

Looking at the sample shots it's also easy to notice distinct vignetting. When it comes to wide angle Sony FE lenses it is a common problem and we wondered how the Sigma would deal with it. A preliminary assessment shows that the problem is noticeable and brightness loss in frame corners amounts to about 3 EV. Of course only the full test of the final specimen can confirm our initial impressions.