Lens review

Viltrox AF 75 mm f/1.2

12 December 2023
Maciej Latałło

10. Autofocus and focus breathing


Autofocus of the tested lens, when joined with the Fujifilm X-T2, isn't completely noiseless because you can hear a delicate whirr of the mechanism. We don't have any reservations concerning the speed because running through the whole range and confirming the focus takes about 0.5 of a second, a very sensible result.

Still, the accuracy of the mechanism made us rather concerned. Even in good light the lens quite often displayed a red square meaning that the focus couldn't be properly set. As if it wasn't enough, the red square, theoretically meaning that the focus could be set without any problems, didn't mean proper autofocus work at all. The number of misses during our test was high indeed, approaching even 15%.

Our findings ceased to be relevant very soon; while we've been testing the lens the producers released their new 1.0.3 version of software and it did improve the performance of the autofocus and made its work in manual mode less jumpy. The focusing mechanism now is much more predictable, it doesn't confirm the focus in place where it shouldn't and the number of misses dropped to near 5-10%. It's still a bit too often but we know the standards are raised really high, taking into account the depth of field, offered by the tested lens.

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We didn't have any problems with front or back focus tendency for a change. Even when we took photos from closer distances the aim was always practically in the middle of the offered depth of field.

Fujifilm X-T2, f/1.2
Viltrox AF 75 mm f/1.2 - Autofocus and focus breathing

Focus breathing

Focus breathing tests show refraiming images as you oversharp them. We conduct such a test by passing manually 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.

After conducting a number of tests now we think we are able to determine some reference points. 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.

The test video of the Viltrox lens is presented below:

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 16% so is on the borderline between high and very high level. It means this aberration might be bothersome and disturbing in many situations and it's not corrected perfectly well.