Studio Tests (Full frame)

The Sigma performs exceptionally well on full frame; it may not quite match the Zeiss Otus 55mm F1.4 for sharpness at maximum aperture, but it outperforms anything else in its class for which we have data, including Nikon's recent AF-S Nikkor 58mm F1.4G. Its extraordinarily low distortion is particularly remarkable - this level of correction is normally reserved for Macro lenses.

Sharpness Sharpness is very impressive indeed. At F1.4 it's unusually high for a 50mm prime, and deteriorates only slightly from the centre to the corners. By F2.8 it's extremely sharp right across the frame, to the extent that these measurements are probably limited more by the EOS 5D Mark III's 22MP sensor than by the lens. There's hardly any change on stopping down to F8, but beyond this the softening effect of diffraction inevitably kicks in. However even F16 should give entirely usable results when extended depth of field is necessary.
Chromatic Aberration Lateral chromatic aberration is extremely low. There might be a tiny bit of green/magenta fringing right in the corners of the frame if you really go looking for it, but it's unlikely to be problematic in normal use.
Vignetting Vignetting is kept well under control, at just 1.5 stops wide open, which is very respectable for an F1.4 prime. The falloff profile is rather gradual too, which tends to make any vignetting less visually objectionable. Stop down to F2, and any vignetting effectively disappears.
Distortion Distortion is astonishingly low, with just the barest hint of pincushion stretching at the extreme corners of the frame. This marks the Sigma apart from other 50mm full frame fast primes, which all tend to show some degree of barrel distortion.

To really appreciate just how good the Sigma is, we need to look at how it compares to other similar lenses (click on the yellow links to open up comparison widgets in a new window). The benchmark right now is the Zeiss Otus 1.4/55, and while the Sigma can't quite match it for outright sharpness right across the frame wide open, it's extremely close. Indeed when tested on the 22MP Canon EOS 5D Mark III, it's clear that the MTF measurements for both lenses are being limited as much by the camera's resolution as by the lens itself, even at maximum aperture. In other respects the gap is also very narrow, with the Sigma having slightly higher chromatic aberration, but less vignetting and lower distortion than the Zeiss.

Now let's take a look at some other premium fast primes. The Sigma is simply much sharper at maximum aperture than the Nikon AF-S Nikkor 58mm F1.4G (despite being tested here on a lower-resolution camera), and has far lower distortion too. We see a similar story compared to the Canon EF 50mm F1.2L USM; the Sigma is sharper, has notably lower later chromatic aberration, and of course practically no distortion at all. It's also worth noting that the 50mm outperforms its much-lauded sibling, the Sigma 35mm F1.4 DG HSM | Art, in every attribute we're measuring here.

Compared to more-conventional 50mm F1.4s, the Sigma also shines. It's substantially sharper than either the Nikon AF-S Nikkor 50mm f/1.4G or the Canon EF 50mm f/1.4 USM at apertures larger than about F5.6, and has lower chromatic aberration, vignetting and distortion than either of these lenses too. It's much the same story with Sigma's previous 50mm F1.4 EX DG HSM; the new model is much sharper wide open, and clearly better in the corners of the frame at intermediate apertures. Of course these lenses are all much less expensive - but this shows why.

One lens that we don't yet have test results for is the Sony Carl Zeiss Planar T* 50mm F1.4 ZA SSM. However with its more-modern optical design, Zeiss branding and high price tag, we'd expect it to be a much closer competitor to the Sigma. Interestingly Sony's FE 55mm F1.8 ZA for its full-frame E-mount mirrorless cameras offers similarly-high optical quality to the Sigma.

Macro Focus

Macro - 191 x 128 mm coverage
Measured magnification: 0.19x
Distortion: Mild barrel

Minimum focus distance*: 37.8cm
Working distance**: 23.4cm
Focal length: 35mm
* Minimum focus is defined as the distance from the camera's sensor to the subject
** Working distance is measured from the front of the lens to the subject

As you'd expect, it's a similar story on full frame to what we saw on APS-C when shooting at the lens's minimum focus distance. The image is a little soft wide open, but the center sharpens up very well by F2.8. Stop down to F8 and the image is extremely sharp across the frame and almost completely free from chromatic aberration. Some slight barrel distortion creeps in, but it's less than you'd see from most 50mm fast primes at more normal shooting distances. This is all very impressive indeed.