Lens Reviews / Sigma Lenses i Lab tested

50mm	$840 average price

Sigma 50mm f/1.4 Art Review

by Imaging Resource | Posted April 4, 2014

When we sat down with Sigma at this year's CES, we got some hands-on time with the lens. The build quality was exceptional, but what really got our attention was Sigma's off-handed remark that they weren't looking to surpass Nikon and Canon, but rather the $4,000 Zeiss Otus 55mm ƒ/1.4 monster.

The Sigma 50mm ƒ/1.4 Art is quite large and bulky with a total of 13 elements in 8 groups, including 1 aspherical and 3 super low dispersion elements. Other optical performance features include a 9-bladed rounded aperture for pleasing and smooth background blur and Sigma's latest Super Multi-Layer Coating to reduce lens flare and ghosting. Focusing should also be fast and quiet thanks to their Hyper Sonic Motor AF system.

50mm is a classic focal length for the full-frame shooter, and after Sigma's astounding 18-35mm ƒ/1.8 Art DC lens, it wouldn't be an exaggeration to say this is one of the most anticipated products of the year. The competition from Canon and Nikon includes garden-variety 50/1.4s on the low end, with Nikon offering the slightly longer 58mm ƒ/1.4 Nikkor on the high end, and Canon the ƒ/1.2 L.

The Sigma 50mm ƒ/1.4 Art lens ships with front and rear caps, a bayonet-mounted lens hood and a sturdy soft case, and is set to be available in Canon EF, Nikon F, Sony A, Sony E and Sigma SA mounts.

So how does the Sigma stack up? In a word, or three: very, very well. Read on to find out more...

(UPDATE, 4/8/14) We've now reviewed the Zeiss 55mm ƒ/1.4 Otus, and the results from both lenses are extremely impressive! We've updated our review of the Sigma below to include comparisons to the Otus where appropriate.

Sharpness
Since Sigma developed this lens with a goal to best the incredibly sharp Zeiss Otus (a $4,000 55/1.4 optic), we've been expecting it to be pretty sharp. Interestingly, though, Sigma president Kazuto Yamaki told IR/SLRgear founder Dave Etchells that they actually traded off just a little sharpness, in order to achieve better local contrast.

Comparing the Sigma 50mm ƒ/1.4 Art lens against other high-end competition from Canon, Nikon, and Sony, it certainly seems like Sigma succeeded in their goals. The lenses we're comparing the Sigma to are the Zeiss 55mm ƒ/1.4 Otus APO-Distagon, the Nikon 58mm ƒ/1.4G AF-S Nikkor, the Canon 50mm ƒ/1.2L USM, and the Sony FE 55mm ƒ/1.8 ZA Carl Zeiss Sonnar T*.

As we had hoped, the Sigma 50mm ƒ/1.4 Art stands up to the Zeiss 55mm ƒ/1.4 Otus very well, meeting or slightly exceeding the optical performance of the Zeiss! In terms of sharpness, the Sigma performs superbly. At ƒ/1.4 on a full-frame camera, the Sigma 50mm ƒ/1.4 Art is just as sharp right in the center as the Zeiss lens, while the Otus shows better sharpness in the corners. The Otus 55mm's blur characteristic is almost perfectly flat, and very sharp everywhere. When you stop down to ƒ/2.8, the Zeiss 55mm and Sigma 50mm show very similar, very sharp and very flat blur characteristics. Looking at our graphs, you may think the Sigma appears slightly sharper, but the difference is so slight, it's essentially negligible.

The Sigma 50/1.4 Art's sharpness holds up very well against the sub-$2,000 competition, as well. At ƒ/1.4 and on a full-frame camera, it pretty well blows all of the others out of the water. The Canon 50/1.2L is pretty sharp in the center, but the corners are extremely soft. The Nikon 58/1.4 is less sharp in the center, and quite soft in other parts of the frame. The Sony 55/1.8 obviously doesn't get to ƒ/1.4 at all, so there's nothing to discuss on that front.

The other lenses all improve at ƒ/2, but so does the Sigma 50, easily bettering all comers, at every point across the frame. At ƒ/2.8, the Sigma's blur characteristic is almost perfectly flat, and quite sharp everywhere. The Nikon 58/1.4 is quite sharp in the center, but still with softer corners, albeit not quite as bad. The Canon 50/1.2 is also quite sharp at the center, with a little corner softness, and the Sony 55/1.8 is fairly flat, but still a bit softer on the left and right sides. At smaller apertures, the Sigma stays very flat and very sharp, with just a hint of diffraction limiting creeping in at ƒ/8, as is the case with the other three lenses as well. The Nikon 58/1.4 never really flattens out, all the way to ƒ/16, while the Sony and Canon optics are both quite flat by ƒ/8.

Sub-frame sharpness results are about what you'd expect, just crops of what we saw in the full-frame bodies. The Nikon improves more than the others, since its sharpness a ways out from the center is so much worse than areas near the center that a lot of its bad behavior just doesn't appear within the sub-frame sensor area.

The Zeiss 55mm Otus lens shows slightly sharper corners on a sub-frame camera at ƒ/1.4, than does the Sigma, but this difference becomes negligible at ƒ/2.

(Ed. Note: Given the extent to which we expect people will be squinting over these results, it's worth noting here again that differences in sharpness associated with a single color level change really aren't discernible visually, no matter how much you might care to pixel-peep real-world images. So please, no angels-on-the-head-of-a-pin arguments over one lens or the other being one shade of pink/purple than the other here :-)

Micro-contrast
In case you were thinking we wouldn't get around to discussing the micro contrast beyond the above, fear not!

Given Kazuto Yamaki's decision to prioritize micro contrast at the expense of sharpness, we had to take a look at this aspect of performance. The results were amazing.

You see, while the resolving power of the Otus technically barely nosed out the Sigma in our blur testing, the perceived sharpness of the Sigma is actually greater than the Zeiss lens. For the most dramatic example of this, take a look at this crop from the upper left corner (mouse over the image to see the crop from the Zeiss 55mm f/1.4 Otus lens):

Mouse over this image crop to show results Sigma compared to the Zeiss.

How can this be? Well, resolution can be defined as the ability to differentiate between closely-spaced transitions from light to dark. The Otus clearly has this in spades.

But the quality of these transitions is important for our perception of sharpness; sharpness and resolution are related to each other, but it's possible for a lower resolution image to actually look sharper to our eyes. Looking at the alternating light/dark lines in the Sigma shot, you can see that it clearly renders them with crisper edges and higher contrast between the light and dark areas.

The other factor at play here is the CA (and perhaps a bit of coma distortion and general veiling flare in the corners), which are poorer on the Sigma than the Otus. This reduced contrast and lightening of the dark target elements where the "purple haze" intrudes on them is interpreted by DxO Analyzer as blur. (Which it is really, just with a different characteristic than the diffuse blur we commonly refer to with that term.) So, while it is technically blur, the image still looks sharper to our eyes than that of the Zeiss, as you can see from the Sigma crop above.

When comparing the blur graphs for the two lenses, another point comes into play, namely that the DxO Analyzer software we're using here measures blur at 17 points across the image, which our graphing software then draws smooth contours to fit. This gives a pretty complete and easily digestible view of a lens's blur characteristics, but we're not seeing every single point in the frame. Within the bulk of the frame, it's unlikely that a lens will do something crazy entirely between measurement points, such that it won't show up in the plots. However, it is possible (as is the case with Zeiss 55/1.4 Otus), that a lens might turn bad at the very edge of its image circle, and not be picked up, because the behavior is outside the measurement area. At the corner-most locations that DxO Measured, the Zeiss settled down pretty well, and is actually a bit better looking than the Sigma, but as you can see from the crops above, the Sigma looks noticeably better in the extreme corners. (And its geometric distortion there is significantly better as well.)

Mouse over this image crop to show results Sigma compared to the Zeiss in the center of the frame (sub-frame).

Turning to the center of the frame, the mouseover image above compares the two lenses on the Canon 7D sub-frame body, chosen because it has smaller pixels than our Canon 1Ds Mark III test body, so it represents more of a challenge for the lenses here. The difference between the two lenses isn't as stark here as in the corner, but the higher local contrast of the Sigma does give it a sharper appearance, even if the resolution is about equal between the two.

All in all, this is a case where the raw test numbers doen't carry the entire message. For our money, we'd go with the slightly higher CA, lower sharpness, but higher micro contrast of the Sigma, even if the two lenses cost the same.

Chromatic Aberration
CA is reasonably well controlled in the Sigma 50mm ƒ/1.4 Art lens, with a very low average value at ƒ/1.4 on a full-frame body, increasing gradually to a still-low value at ƒ/2.8 and remaining constant as you stop down further. The maximum CA is a bit higher at ƒ/1.4 and ƒ/2, decreasing to about ƒ/4. This difference between maximum and average CA means that the Sigma's CA is confined to a small portion of the frame, mainly in the corners.

If there were any weak point in the Sigma's performance compared to the competition, it would probably be CA, as both the Nikon and Sony beat it on that score. The Canon 50/1.2 is higher in both maximum and average measures, though.

The Zeiss 55mm Otus, not surprisingly, shows very well-controlled CA properties; with consistently low CA across the entire aperture range on full-frame and sub-frame cameras. In our test images, we saw practically zero CA in either the center of the frame or up in the corners, at ƒ/1.4 and ƒ/8, whereas the Sigma showed minor CA in the corners at ƒ/1.4.

On sub-frame bodies, the results are somewhat similar, although the Sigma's maximum value is lower wide open, and both max and average values are a little higher at ƒ/2.8 and above. The Canon 50/1.2 shows considerably worse maximum CA on an APS-C frame. (It's quite common for lenses to show worse CA on smaller-frame bodies, since the CA is measured relative to frame height, and a given displacement between the colors will correspond to a larger percentage of the smaller frame size.)

Shading (''Vignetting'')
Shading is very common on large-aperture lenses when shot wide open, so it's not surprising to see a fair bit of it in the Sigma 50/1.4 Art. Interestingly, the Sigma 50mm ƒ/1.4 Art lens displays less vignetting than the Zeiss 55mm Otus when shot wide open, with under 1EV of light falloff, compared to the Zeiss at a smidge below 1.25EV.

As for the other 'affordable' competition, the Sigma handily beats both the Canon and Sony competitors in this area, and the Nikkor only just edges it at ƒ/1.4. The Sigma easily beats even the Nikon by ƒ/2, although interestingly, the Nikon shows less shading at ƒ/2.8 and higher than any of the other models we're discussing here. That said, though, light falloff with the Sigma is less than a quarter of a stop at ƒ/2.8 and higher on a full-frame body. On an APS-C body, the Sigma's maximum shading is just over a quarter of a stop, and less than a tenth of a stop at ƒ/2 and above.

Distortion
The Sigma 50mm ƒ/1.4 Art lens easily carries the day here, with almost immeasurable geometric distortion -- even compared to the Otus! (Average distortion is pretty much dead-zero, max distortion shows the tiniest hint of pincushion.)

On a full-frame body, the other lenses all show some degree of barrel distortion, with the Nikkor the most, at about 0.5% max and 0.2% average, and the Canon next at perhaps 0.4% and 0.2% respectively. The Sony and Zeiss 55mm Otus are practically tied for the best of the others, with around 0.2% max and under 0.1% average.

On sub-frame bodies, the Sigma's distortion is also near zero (no surprise), as is the Zeiss Otus in this case. Distortion of the Canon and Nikon are both reduced, but the other Sony's characteristics change a little. This is often the case with highly-corrected lenses like these, in that the distortion doesn't just rise continuously as you move out from the center. For instance, if you look closely, you might find a little barrel in the center, some pincushion a bit out from there, and barrel again in the corners - or some other combination, depending on the lens in question. In the case of the Sony 55/1.8, the maximum distortion is a slight pincushion effect, while the average is a slight barrel effect. Both are under 0.1%, though, so could be considered negligible.

By any measure, and regardless of frame size, the Sigma 50mm ƒ/1.4 Art's distortion performance is just phenomenal.

Focusing Operation
The Sigma 50mm ƒ/1.4 Art lens focuses quickly -- and practically silently -- thanks to its Hyper Sonic Motor electrical AF system. However, it doesn't feel like the fastest AF in the world when racking all the way from minimum to infinity focus, which takes around one second, or perhaps a hair longer. Focusing in everyday scenarios with subjects in the intermediate focus distances felt very fast and accurate, though, and at times nearly instantaneous.

Of course, there's manual focusing as well, plus full-time manual focus override when using autofocus. The focus ring rotates very smoothly with enough resistance to prevent accidental adjustments but easy enough to adjust with a thumb and forefinger. The ring has soft stops at both minimum and infinity focus distances and provides a little over 90 degrees of rotation.

Macro
This lens isn't specifically built for macro shooting with a maximum magnification ratio of 0.18x (1:5.6) and a minimum close-focusing distance of around 40cm (1.3 ft.). Therefore it's not great for true macro shooting, but can still focus relatively close, making it great for up close portraits, products shots, etc.

Build Quality and Handling
A lightweight "nifty fifty" this lens is not! The Sigma 50mm ƒ/1.4 DG HSM "A" is a serious lens, with serious weight and build quality. Like the other Global Vision lenses before it, the new Sigma 50mm ƒ/1.4 Art lens is very well built, making use of their Thermally Stable Composite material, that despite technically being a form of polycarbonate plastic, looks and feels more like metal (and shares similar thermal properties to aluminum, as well). The barrel design is finished in a smooth matte black texture, with a nice, thinly-ridged texture along the underside for some grip. The large 1.5-inch-wide focus ring has a similar ridged texture embossed into the thick, rubberized grip. If you've used any other Sigma Global Vision lenses, such as the 24-105mm ƒ/4 or 35mm ƒ/1.4, you'll be familiar and undoubtedly impressed with the design and build quality of this lens.

Other optical performance features include a 9-bladed rounded aperture for pleasing bokeh and Sigma's Super Multi-Layer Coating to reduce lens flare and ghosting.

Being a prime lens, the lens is a pretty straightforward affair in terms of bells and whistles. A focus distance window complete with a distance scale and depth of field markings sits on top of the lens. There's also a MF/AF switch on the left side, which has a nice, solid feel to it -- no risk of accidentally toggling focus modes. The reversible polycarbonate lens hood feels very solid with a rubberized bayonet mount that snaps in place with satisfying click -- no issues with wiggle or play.

We mentioned "serious weight" and we're not kidding. This lens is large and bulky, with a total of 13 elements in 8 groups, including 1 aspherical and 3 super low dispersion elements, all inside a large diameter barrel that accepts 77mm filters. Whereas competing lenses from other manufacturers, such as the Nikon 58mm ƒ/1.8G or Canon 50mm ƒ/1.2, the Sigma 50mm ƒ/1.4 Art are pretty compact and lightweight, the Sigma is no such thing. You'll be toting around a prime lens larger and heavier than many zooms, at just shy of four inches long and around 810g (28.6 oz.) in weight.

On the other hand, the only lens that manages to best Sigma's optical performance is the significantly larger and heavier Zeiss Otus 55mm ƒ/1.4. Make no mistake though, stellar optical performance exacts a price: this lens is definitely not the typical lightweight, go-anywhere 50mm ƒ/1.4.

Our full-frame test camera for Canon lenses is the 1Ds Mark III, which is far from a lightweight camera on its own. With the Sigma 50mm lens mounted to that camera, it's a heavy combo. Even on our smaller Canon 7D body, it makes for a pretty hefty pairing. However, if you're used to using large lenses and larger cameras, the weight and bulk of this lens is not overbearing or awkward. It actually feels more akin to using something like a 24-70mm ƒ/2.8 lens (in fact, this Sigma 50mm is almost the same weight as the Canon EF 24-70mm ƒ/2.8L II USM) and is nicely balanced on both the large, full-sized DSLRs as well as medium-sized ones.

Alternatives
On the Nikon side, you have basically three options:

The affordable 50mm models in ƒ/1.4 and ƒ/1.8 versions, available for around $450 and $220, respectively. That's a significant savings on the price of the Sigma. The image quality of these models, while far inferior to Sigma's triumph, aren't terrible when stopped down - but stopped down isn't what the Sigma is all about.

The slightly longer 58mm ƒ/1.4 Nikkor available for $1,700. Even though Nikon pushed the focal length on this one, results are only marginally improved from the $450 50mm ƒ/1.4 mentioned above. We really can't recommend this lens over Sigma's 50mm ƒ/1.4 Art.

On the Canon side, your options are similar:

Like Nikon, Canon offers lower-cost 50mm options in ƒ/1.4 and ƒ/1.8 variants, for about $400 and $100, respectively. These lenses will struggle wide open, but perform well when stopped down, though you'll again need to get to ƒ/2.8 and ƒ/4.0 before things become tack sharp.

On the high end, Canon offers a direct focal length-competitor in the $1,700 50mm ƒ/1.2 L. While you gain a half-stop advantage, this lens is quite soft in the corners, even at ƒ/1.4. Light falloff and CA are both factors that also put it solidly behind the Sigma. Here too, the advice is easy: buy the Sigma 50mm Art.

Carl Zeiss offers the $4,000 55mm ƒ/1.4 Otus, which matches up more evenly to the Sigma. While this lens is a sharpness monster and edges out the Sigma in CA, the Otus falls to the Sigma in several ways. First, though the Sigma suffers from slower autofocus than some competitors, the Otus gives you no such option. Second, the Sigma has notably better vignetting and optical distortion than the Otus. Third, the Sigma is significantly smaller and lighter. Senior Lens Technician, Rob Murray, commented that the Otus 'Feels like someone took a coffee thermos and poured molten glass into it.' That's obviously an exaggeration, but the thing is massive. Finally and most significantly, the Sigma comes in at less than a quarter the price of the Otus. There are certainly good reasons to choose the Otus over the Sigma, but we doubt if many photographers will make this decision.

Conclusion
The Sigma 50mm ƒ/1.4 Art is the most exciting lens we're likely to review this year. All competing lenses from Canon and Nikon fell short when compared to the resolving power of the 50mm Art. Compared to the mighty Zeiss 55mm ƒ/1.4 Otus, the Sigma holds its own, displaying nearly identical results! Even though it has a higher price than the standard 50/14 offerings from Canon and Nikon, this lens is easy to recommend. Put simply: it trounces any similar model available for less than $4,000. And since it comes in significantly cheaper than the best of Canon and Nikon, Sigma has made a friend of every full-frame shooter in the land.

Product Photos

Sample Photos

Check out a set of gallery photos taken by Rob, our senior lens technician, using the Canon 1Ds Mark III. They can viewed, including full-resolution versions, over on our Flickr page.

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

UPDATE (4/8/14): We have now added our lab sample images. Click through on the links below.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.