Tamron SP 45 mm f/1.8 Di VC USD review - Autofocus

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Tamron SP 45 mm f/1.8 Di VC USD

13 October 2015

Arkadiusz Olech

10. Autofocus

The autofocus mechanism of the Tamron 1.8/45 is practically noiseless; unfortunately it cannot be called very fast. Running through the whole distance scale and finding the proper focus position takes a bit over one second. Still you have to remember that the minimum focusing distance of this lens amounts to 0.29 of a meter so its scale is wider than that of its rivals. For example the Sigma A 1.4/50 focuses from 0.4 of a meter and if you set such a value on the scale of the Tamron and try to focus on an object positioned further away from the camera the time needed to find the focus will shorten to about 0.7 of a second. Still it is a result worse than that of the Sigma which motor speed was below 0.5 of a second. You should also mention the fact that the Tamron’s focusing mechanism performed equally on both bodies used in our test (the D3x and the D7000).

While taking sample shots and testing the lens in our studio we didn’t notice any serious problems concerning the accuracy of the autofocus. Most of photos were sharp; more significant misses happened once every several dozen exposures.

As we deal here with a new construction from an independent producer we also decided to test the autofocus in a more thorough way. First we took 30 photos of our resolution testing chart by f/1.8, setting the focus each time anew. The results were very good – they ranged from 1356 to 1442 LWPH for the vertical profile measured on JPEG files so their dispersion was slight.

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In the next step we repeated that procedure but with employing the f/2.8 aperture. What’s interesting the dispersion was bigger here. Even though most of results fitted in a range from 1511 to 1690 LWPH the lens had two slip-ups generating values of 1305 LWPH.

Still we didn’t have any special problems with front or back focus tendencies – on both bodies the lens performed as it should and didn’t need any microcalibration.

Nikon D7000, f/1.8