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Autofocus

The Sigma C 20-200 mm f/3.5-6.3 DG is equipped in a linear motor called HLA (High-Response Linear Actuator) so its autofocus is supposed to be flash quick and very quiet.

We tested the focusing mechanism of the Sigma by joining it with the Sony A7R IIIa and the Sony A7R V cameras. In both cases the mechanism as indeed noiseless and quick. First we checked it in the AF-S mode. At 20 mm running through the whole distance range and confirming the focus was flash quick, taking 0.2 of a second at most, no matter from what end you started. At 200 mm this time increased to 0.5-0.6 of a second. The situation changed a bit after choosing the AF-C mode. The performance at 20 mm remained as fast as previously, it would be difficult to speed it up even more, but the working time at 200 mm was shortened about two times. You can say without exaggeration that the speed of the Sigma's 20-200 mm autofocus is excellent indeed.

When it comes to the accuracy, the focusing mechanism performed without any problems as well. We used this lens extensively, attaching it mainly to the Sony A7R IIIa in our studio and to the Sony A7R V outside. We had a lot of shots to make because we wanted to show its performance at different apertures and focal lengths, both for uncorrected and corrected files. In all situations the autofocus performed properly well, never providing any reasons to complain.

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Photos below prove that, no matter what focal length you apply, the Sigma C 20-200 mm f/3.5-6.3 DG doesn't have any front or back focus tendencies.

A7R V, 50 mm, f/5.0

A7R V, 100 mm, f/6.3

A7R V, 200 mm, f/6.3

Focus breathing

Focus breathing tests show reframing images as you oversharp them. We conduct the test by manually passing from the minimum focusing distance to infinity with the aperture stopped down; then we check how the field of view of the lens changed as a result.

A frame change ranging from 0 to 5% we consider to be low. Between 5 and 10% you can speak about medium levels. Usually such values constitute also the maximum efficiency level of any breathing compensation algorithms, present in some bodies. Between 10 and 15% focus breathing is high, above 15% its level can be called very high.

Below we present the test video of the Sigma lens:

On the basis of the recording above, comparing freeze-frames before and after oversharpening, we can estimate that the breathing of the tested lens amounts to about 4 % at the shortest focal length and about 1% at 200 mm. In both cases you deal with a slight level of this aberration and the constructors of this zoom should be really praised for it.