Lens review

Tamron SP 15-30 mm f/2.8 Di VC USD

17 March 2015
Arkadiusz Olech

4. Rozdzielczość

The resolution test (resolution meaning the MTF50 values) of the Tamron 15-30 mm f/2.8 Di VC USD was based on RAW files from the Canon EOS 5D Mark III. In the case of that reflex camera the decency level is situated near 30-32 lpmm and the best fixed focus lenses can reach as high as 44-47 lpmm.

First let’s check how the tested lens performed in the frame centre – the results at 15, 22, and 30 mm are presented below.

Tamron SP 15-30 mm f/2.8 Di VC USD - Rozdzielczość

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Three things stick out immediately. Firstly – a very even performance at all focal lengths. Here the Tamron fares a tad better than the Nikkor 14-24 mm f/2.8 because Nikkor’s shortest focal length lagged behind the rest. Secondly, excellent results already from the maximum relative aperture. Thirdly, high maximum level of MTFs – by f/4.0 –5.6 the Tamron is able to get near to 45 lpmm, a value worth of a good ‘prime’. There is really nothing to criticize here, the tested lens should be only praised.

How does the lens compares with its competitors? The Canon EF 16–35 mm f/4L IS USM, tested by us not so long ago, also was able to reach near 45 lpmm, but its 35 mm focal length lagged behind the rest noticeably. The Canon EF 16–35 mm f/2.8L II USM was tested on the EOS 20D whose MTFs are by 1–2 lpmm lower than in the case of the EOS-a 5D MkIII. After compensating that difference the maximum achievements of the Canon and the Tamron are practically identical but at the maximum relative aperture, especially by f/4.0, the Tamron fares better, showing a more even performance. A direct comparison with the Nikkor 14–24 mm f/2.8 is difficult because that lens was tested on the sensor of the Nikon D200 and the best fixed focal lenses, tested on that camera, could reach 47-49 lpmm so about 2 lpmm higher than in the case of the Canon 5D MkIII. When you take that into account both lenses fare similarly at the longer end of the focal range but a comparison between the 15 mm of the Tamron and the 14 mm of the Nikkor is more favourable for the former.

Overall assessment of the frame centre performance is such that the Tamron prevails over the Canon and the Nikkor but only slightly. The differences are really small but it is quite understandable; the rivals were able to achieve a really high level of performance, presenting good or even excellent values. Still optics specialists from Tamron should be congratulated – they managed to beat all the rivals by the skin of their teeth. A round of applause!

Now let’s check the results on the border of the APS-C/DX sensor, consulting the graph below.

Tamron SP 15-30 mm f/2.8 Di VC USD - Rozdzielczość

Once again the evenness of the performance sticks out at once. In fact only one point, at a combination of 15 mm focal length and f/2.8 aperture, lags behind all the rest and our reservations concern only that position - the lens doesn’t reach the decency level there. An identical situation could be observed in the case of the Nikkor 14-24 mm with one difference: at the shortest focal length the results lagged behind those of other focal lengths and the decency level could be exceeded but only slightly. The Canon 16-35 mm f/2.8 fared very badly on the edge of the frame; in order to get useful images on the small APS-C sensor, it had to be stopped down to near f/5.6. In that category the Tamron is slightly better than the Nikkor and simply outclasses the Canon.

Now it’s time for the performance on the edge of full frame – an appropriate graph is presented below.

Tamron SP 15-30 mm f/2.8 Di VC USD - Rozdzielczość

Here the distribution of the points is the greatest. The 22 mm focal length fares the best, providing even at the maximum relative aperture a decent image quality. The shortest focal length is not bad either but only on stopping down; with the lens wide open, it is actually the weakest of all. At the maximum focal length and by f/2.8 the MTFs are a tad below the decency level but in the f/4-f/11 range they manage to rise a bit above it. Taking into account the difficulty level of the task the Tamron optics specialists had to face it’s enough to say that, on the very demanding edge of full frame, by f/2.8 and f/4.0, the results of the tested lens across the whole focal range are better than those of the Canon 16-35 mm f/2.8 on the edge of the smaller APS-C sensor. No comment.

At the end of this chapter traditionally we present crops taken from photos of our testing scene in the frame centre. It’s worth reminding here that these are JPEG files saved along RAW files we used for the analysis above.

Canon 5D MkIII, JPEG, 22 mm, f/2.8
Tamron SP 15-30 mm f/2.8 Di VC USD - Rozdzielczość
Canon 5D MkIII, JPEG, 15 mm, f/5.6
Tamron SP 15-30 mm f/2.8 Di VC USD - Rozdzielczość