Lens review

Sigma 85 mm f/1.4 EX DG HSM

20 December 2010
Arkadiusz Olech

4. Image resolution

The resolution test of the Sigma 1.4/85 was based on RAW files from the full frame Nikon D3x. The measurement errors ranged from 0.2 to 1.5 lpmm.

Sigma 85 mm f/1.4 EX DG HSM - Image resolution

Let’s only remind here that in the case of the tests conducted on the D3x the best „primes” reach as high as 46-47 lpmm and the decency level is set near the area of 30-31 lpmm. How the Simga performs in the frame centre? At the maximum relative aperture it has a result a bit over 30 lpmm so the value considered by us as useful. It is well within the margin of error so the result is exactly like that of the Nikkor AF-S 1.4/85 and by 2 lpmm higher than that of the Samyang 1.4/85. The expensive and fast Canon EF 1.2/85 by f/1.4 achieved over 33 lpmm but we must remember it was tested on the Canon 1Ds MkIII and the MTFs from that camera are by 1-2 lpmm higher than those from the D3x. If we take this fact into account the advantage of the Canon over the Sigma by f/1.4 is only nominal.

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The flash-quick improvement of the image quality on stopping down is a very strong point of the Sigma. By f/2.0 we already get the result of over 39 lpmm - the same the Nikkor AF-S 1.4/85 reached by f/2.8! It is also by ca. 8 lpmm more than the result of the Samyang and once again only a tad less than in the case of the Canon 1.2/85.

By f/2.8 and f/4.0 the situation doesn’t change. The Sigma is still better than the Samyang and the Nikkor, faring just a tad worse or the same as the Canon. From about f/5.6 the results of the Sigma the Canon and the Nikkor become practically undistinguishable – only the cheapest Samyang lags behind because it doesn’t exceed 40 lpmm at any aperture.

To make our comparisons complete we can also include the results of the Sony/Zeiss 1.4/85. It’s true its test was conducted on the A100 but we also got result on a full frame 24 Mpix sensor of the A850 model because they were published in the article concerning the history of the Alfa mount (only in Polish on Optyczne.pl). You must remember, though, that the MTF values from the A850 are by about 3-4 lpmm lower than those from the D3x. Even if you add these 3-4 lpmm to the results of the Zeiss the Sigma still remains sharper at every aperture from f/1.4 to f/5.6!

Let’s pass to the frame edge performance on the APS-C/DX sensor. At the maximum relative aperture the Sigma is not useful yet. It’s enough to close it down by about 0.5 EV to get full usefulness, though. By f/2.0 the tested lens gives a result on the level of 34 lpmm. Then the values get even better because in the f/2.8-f/11 range we achieve results of 40 lpmm or a tad lower. You must notice, though, that the Nikkor wasn’t praised here for a splendid frame edge performance without a reason. At the maximum relative aperture it fares better than the Sigma but the Sigma prevails by f/2.0 and by f/2.8; after that both lenses perform equally well.

When we move to the edge of full frame the Nikkor is better than the Sigma. The latter must be closed down to near f/2.8 to get fully useful results and the Nikkor was useful already by f/2.0. Although the Sigma loses to the Nikkor here it fares significantly better than the expensive Canon 1.2/85 and as good as the Zeiss. The fact that it is also better than the four times cheaper Samyang shouldn’t surprise us at all.

To sum up in the frame centre the Sigma is only slightly worse than the expensive and fast Canon 1.2/85. On the edge of the frame it loses to the Nikkor but it is better than the Canon 1.2/85 and similar to the Zeiss. Such a performance is simply sensational, especially keeping in mind the fact that the Nikkor will cost us about 800 $ more and the Sony/Zeiss- ca. 450 $ more; the Canon is more than two times as expensive as the Sigma.

At the end of this chapter we present traditionally some crops from our test chart’s centre, taken from JPEG files saved along with RAW files.

Sigma 85 mm f/1.4 EX DG HSM - Image resolution