Samyang AF 35-150 mm f/2-2.8 FE
9. Autofocus and focus breathing
Autofocus
The Samyang AF 35-150 mm f/2-2.8 FE is equipped in a linear autofocus stepping motor (STM) that is supposed to ensure you a noiseless work of the focusing mechanism. We checked it using two bodies, the Sony A7R IIIa and the Sony A7R V.When it comes to noise level we have no reservations whatsoever - the mechanism is indeed very silent. The speed results are rather ambiguous. With the lens attached to the older A7R IIIa the autofocus performance was a bit random. When everything went well, at the 35 mm focal length running through the whole range and confirming the focus could last 0.4-0.5 of a second and at 150 mm it reached 0.6-0.8 of a second. Unfortunately, from time to time the lens had some glitches and froze, its autofocus being at a loss what direction it should go to. The photographer might be puzzled in such a situation – you simply aren't sure whether the lens registered the fact of pressing the shutter release or not. Still if you keep pressing the autofocus revives and moves towards the right direction. I admit it is not a performance you expect from a good quality lens.
What's interesting, that effect was practically absent when we attached the tested lens to the newer Sony A7R V. Still the overall speed was similar to the speed we observed with the older body.
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When it comes to the accuracy of the mechanism we also have many reservations. Using the newer A7R V camera didn't help here at all because the number of misses remained very high, reaching near 15%. In this aspect the tested Samyang has to yield to the rival Tamron.
Photos below show that the tested lens didn't have any front or back focus tendencies – everything looked properly well no matter what focal length and what body we used in our test.
A7R IIIa, 35 mm, f/2.0 |
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A7R IIIa, 85 mm, f/2.8 |
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A7R IIIa, 150 mm, f/2.8 |
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A7R V, 35 mm, f/2.0 |
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A7R V, 85 mm, f/2.8 |
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A7R IIIa, 150 mm, f/2.8 |
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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.
The test video of the Samyang lens is presented below: