Leica APO-Summicron-SL 35 mm f/2 ASPH. review

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Leica APO-Summicron-SL 35 mm f/2 ASPH.

10 February 2026

Maciej Latałło

10. Autofocus and focus breathing

Autofocus

The autofocus of the APO-Summicron 2/35 joined with the Panasonic Lumix S1R II is noiseless – all you can hear is a tiny whirr of moved elements.

The speed doesn't make you bowled over because running through the whole distance range and confirming the focus takes about 0.6-0.7 of a second. This value depends very weakly on the direction of work and lighting conditions.

Still, the accuracy of the DSD mechanism should be praised. The lens didn't have almost any misses, no matter whether we used it in our studio or outside – it's certainly a performance worth its journalistic parameters.

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We didn't notice any problems connected to front or back focus tendencies.

Panasonic S1R II, 35 mm, f/2.0

Focus breathing

Tests of focus breathing show reframing images as you oversharpen 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 also constitute 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 Leica 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%. It fits the levels we consider to be slight and not bothersome in practical uses.

We get here a quite interesting situation with Leica being very inconsistent when it comes to their APO-Summicron-SL series. From such big and complex constructions you would expect proper correction of focus breathing and the 2/35 model doesn't disappoint you. Unfortunately, its 2/75 brother didn't manage to do it, with focus breathing exceeding 20%.