Lens Review and field test: Sigma 50mm/F1.4 HSM DG ART lens

INTRODUCTION

I'm really not sure why Sigma has a bad rap in India. Practically every other photographer seems to have some silly cautionary tale about buying or using Sigma lenses
From what I can tell, it's only hearsay, since none of the naysayers seem to have either owned or used any Sigma lenses.

Unlike the gossipers, however, I've actually used and owned a couple of Sigma lenses (the 105mm/2.8 macro and the 12-24mm/4.5-5.6) and have found them both to be excellent, optically matching or exceeding their Nikon or Canon counterparts. And at a lower price, to boot.
So when the PR company that represents Sigma in India called and asked whether I'd be interested in reviewing their 50mm Art lens, I said that of course I would be.

The Sigma Art lenses are their flagship product line. Beautiful to look at, with the ability to make some equally beautiful images.

The Sigma Art lenses are their flagship product line. Beautiful to look at, with the ability to make some equally beautiful images.

With it's Art Line of lenses, Sigma's positioning itself as a top-notch lens manufacturer, setting their sights pretty high. The 50mm/1.4 isn't competing with Canon or Nikon 1.4s.
It's competing with the likes of the revered 55mm/1.4 Zeiss Otus, a lens that is touted as "the best standard lens in the world" by Zeiss.

Which is a tad self-proclamatory, if you ask me. Humility, Zeiss. Can you even autofocus? Tsk.

Compared to the Otus, the difference in cost is substantial: the Sigma retails for around Rs. 63,000 (or $950), and while the Otus isn't even listed on popular Indian e-commerce portals, it should cost 4 times as much: $4,000 or thereabouts.

It's worth noting that both Canon's and Nikon's 50mm/f1.4s are considerably cheaper. They're both priced at around Rs. 21,000, i.e. approximately 1/3rd of Sigma's asking price for the 50 mm Art.

Sigma claims that this lens is a "pro level performer for shooting everything including portrait photography, landscape photography, studio photography and street photography", so I put it through its paces to see if that was true.

If you'd like the short version right here, the lens mostly holds up to those claims.

As a final introductory note, the lens apparently ships with a hood, but Sigma didn't provide me with it, so all photos herein have been taken without one. A shame, since there were situations where I could have used it, I think.

Sigma's newer lenses can now also be tweaked, and the firmware can be updated if you purchase a USB dock separately. They didn't provide me one of those, either. Probably a good thing, since at the time of reviewing I had a tonne of other work on my plate.

On with it, then:-

TECH SPECS

Lens Construction 13 Elements in 8 Groups
Angle of View 46.8º
Number of Diaphragm Blades 9
Mininum Aperture f16
Minimum Focusing Distance 40 cm / 15.7 in
Filter Size (mm) 77 mm
Maximum Magnification 1: 5.6
Dimensions(Diameter x Length) 8.636 cm x 9.906 cm
/ 3.4 x 3.9 in
Weight 815 g

BUILD QUALITY AND CONSTRUCTION

Before I made the switch to Nikon, I was using Konica-Minolta gear, and my lens of choice for table-top product photography used to be the wonderful Sigma 105mm/f2.8 1:1 macro.
It was the only third-party lens that I was using at the time: all other lenses in my kit were manufactured by Minolta.

Unfortunately, once I switched to Nikon, that particular lens wasn't immediately available in the market, else I'd have bought it in a jiff. So I bought a Tamron 90mm/f2.8 instead; another great third-party macro. I'm fairly happy with it, despite the slightly shorter focal length and working distance. It more or less matches the Sigma in terms of optical quality.
Build quality, however, is another story. The Sigma macro wins hands-down in that department.

...and that's the first thing that struck me (well, other than its size -it's huge! But more on that in a bit) when I first removed the Sigma 50mm/f1.4 DG HSM ART lens from its nicely-padded soft lens pouch. It definitely deserves the "Art" tag.
I don't usually throw around words like "excellent", but there's really no other word to describe the build quality of this lens. It looks and feels like a premium product. As it should, for the asking price.
The chassis is a combination of a metal alloy and what Sigma calls a "thermally stable composite". I don't know what that means, but the finish is lovely.
 

This lens is big. And heavy. And solid. And big.

This lens is big. And heavy. And solid. And big.

Three points worth noting here:

  1. With a count of 13, this has more lens elements than any other 50 mm in the market. Three of these elements are SLDs,  which are specifically for minimising chromatic aberration. Even the Zeiss Otus 55mm/f1.4 has 12 elements, so Sigma's really pushed beyond some boundaries here.
  2. The 9 bladed diaphragm makes bokeh nearly circular, wide open or stopped down.
  3. At 815 g, this is also the heaviest 50mm out there. It weighs nearly as much as a Nikon D750 with a battery and SD card (840 g). Only the Otus weighs more (and is bigger, too), but that's a 55 mm.

What about size? It's big. Not just big, but, like, big.

At 9.9 cm / 3.9 inches, this lens dwarfs all other 50mms. It's almost twice as big as most other 1.4s and almost three times as large as some 1.8s.

Is the weight or size an issue while shooting? I'd have to say no. Well, for the most part.

The one downside to its bulk is when you use it for street photography: other than the fact that it gets heavy after, say, about an hour of hand-holding, it's also really obtrusive. Meaning, easily noticed by potential street subjects.

Whether you're a master of being discreet or not, there's just no way you can inconspicuously create candid frames for a subject that's close to you, even with a smaller body like a D90. I tried, and although I snuck in a few good photos, almost everybody that I pointed the camera at noticed me, unless they were already preoccupied.

Slap it on a Nikon D4 or a Canon 1Ds and you might as well be walking around in a gorilla suit. Regardless, if you're a capable street photographer, the lens does well. Just don't take it to a place where you know you need to be discreet. Anyway, street photos comin' up, along with:

AUTOFOCUS PERFORMANCE

"Snappy" is the first word that comes to mind here, thanks to the hypersonic motor, or "HSM" for short.
Autofocus is quick even in low light, and the HSM ensures that it is also quiet. No whining or whirring "whEEEEkhEEEE" sounds, thank you. Also, I should mention that in the entire time I used it, there wasn't a single time where the lens really 'struggled' to focus, even in heavily back-lit situations.

Unfortunately, there's also a caveat. I'll come to that shortly.

To test autofocus performance (and to test Sigma's 'pro-level street lens' claim), I took the 50mm/1.4 coupled with a D90 down to the beach. There's always a lot of fast-paced activity on the beach. Cricket, joggers, people exercising etc. Situations that kit zooms might find difficult to track.

But even for fast-moving subjects, autofocus was a breeze. It's easily the fastest-to-focus-confirmation lens I've used thus far. There's a caveat like I said, but after a few images that illustrate the point:

Now, the caveat:
There's a documented problem with AF on this lens, and although 99/100 frames were fine, I did get to experience it first-hand.
On seemingly random but rare occasions, I'd receive in-camera AF confirmation and subsequently take a photograph.
To my disappointment, I'd later find that the lens had somehow "slipped": focus would be off ever so slightly. This happened more than once and I know it's not the camera, because ensuring that camera AF is accurate is one of the first things I do when acquiring a new body.
(hint: all you need is a ruler/scale)
Upon Googling it, I found this to be a common complaint with the 50 mm Art, for Canon and Nikon users alike. Apparently it has something to do with off-center AF sensors throwing the lens' autofocus out of whack. I didn't go through all the forum threads or literature about it, but if you search for "Sigma 50mm f1.4 ART autofocus problem", you'll get a plethora of results, and loads of advice.

This is rather unfortunate, because the lens excels in practically every other department. One is already dealing with razor-thin depth of field when shooting wide open at f1.4, so any deviation will cause a significant shift in the front focal plane. Apparently Sigma is aware of the problem and is working on a fix, so hopefully we'll see one soon.
For now though, if you're thinking of picking up this particular lens, try and test it first if you can. The sample that I received for the review performed admirably well; out of hundreds of photos, I only experienced this a couple of times. I'd consider that an acceptable loss.
However, some users have reported more frequent misses, with the focal plane shifting to the front.

Example below, along with what it should look like when everything's dandy:

Since we broached the topic, let's move on to...

IMAGE QUALITY, CHROMATIC ABERRATION, SHARPNESS

Rather than concentrate on yawn-inducing charts and graphs, I wanted to see how well the lens performs in the field. If you are interested in the charts and graphs, DxO Mark has put it through some tests here (tested only on a Canon body), and Sigma Rumors has a comprehensive list of reviews here.
Charts and graphs galore if you need 'em.

After looking at the specs, I had a bunch of questions that needed answering.
How good are the SLDs? Do they really kill chromatic aberration? Do you get your money's worth in sharpness and overall image quality? Is the bokeh pleasing? How does it handle flare?

Personally, I've always found some chromatic aberration (or CA) when using any lens wide open, regardless of optical design.
The thing is, most photographers will pick up a fast lens for the ability to shoot it wide open, so it's really a matter of how much of a problem CA is in that situation.

And Sigma has minimised CA very well here, those SLDs do their job.
I had to really push limits in order to create a pronounced effect. Here's a photo that tests flare and CA simultaneously:

More than the CA reduction, what I'm really impressed with is how well the lens handles flare. Direct sun in that coconut tree, and no discernible flare effects in the image. A less capable lens would likely have had the entire bottom-half of the frame engulfed in blue and purple overtones.

As for the chromatic aberration itself, it's easily corrected in Photoshop.

While it handles chromatic aberration well, it's still visible in high-contrast situations that aren't quite as extreme as in the example above. The CA often seems to affect defocused elements rather than the sharper areas.

Honestly, that's preferable to CA that affects the focal plane, because it would then reduce sharpness when corrected.

Here's an example.

I think this also answers "How sharp is it?" adequately (answer: you're likely to cut your thumb), but since this is a review and I'm not known for brevity, I thought I'd also test Sigma's claims about this being a pro-level portrait lens and kill two proverbial birds with one piece of glass. Y'know, since I'm a professional and everything.

The Sigma 50 mm 1.4 Art lens is tack sharp when wide open, which is ideal for portraiture, whether that's commercial, editorial, candid, or photos of the internet's favourite animal. This is the sharpest lens I've ever used.
Moreover, while I didn't shoot a graph for testing it, the lens also exhibits very low distortion. Faces didn't appear bloated even when I filled the frame with them at minimum focusing distance. The 50mm/1.8 Nikkor in comparison makes faces appear larger.

Here's a gallery of portrait samples, all shot at f1.4, with no retouching and minimal adjustments in Adobe Camera Raw:

BOKEH

All that sharpness comes with one trade-off, though: slightly-to-moderately distracting bokeh.

Many people fuss over bokeh, the quality and appearance of the out-of-focus areas.
Are they creamy or distracting? Do you get smooth, easy transitions from the focal plane, or is it jarring? Do the out-of-focus elements have noticeable hard edges?
Bokeh is often over-discussed, but it is worth discussing nevertheless.

Especially with the Sigma, because its sharpness is clearly a double-edged sword.
It's so sharp that the out-of-focus elements can indeed be a little jarring. In some of the portraits above, you might have noticed that the defocused greenery is a little ...well.. sharp. A tad more well-defined than I'd like to be, with halos at the edges in some cases.

This actually worsens as you stop down. Bokeh can range from slightly distracting at f1.4 to say f1.8, but once you go past f2.0, it starts getting sharper than I'd like it to be.

Here's what I mean:

Now don't get me wrong, this isn't a complaint in as much advice about how to best use the lens to get past this drawback.

Also, this doesn't mean that you can't get beautiful, creamy and dreamy bokeh. You can, you just need to get your subjects as close as possible, shoot close to wide open, and reduce specular highlights in the background if you can.
Since I provided some criticism, I think it's only fair to also provide examples where the bokeh really shines, so here goes:

CONCLUSION

This is a fast, uber-sharp lens that really can compete with the likes of some of the best optics available in the market today. I can confidently say that the lens lives up to Sigma's claims of being a pro-level all-rounder.
Even up close and personal, there is little distortion. Chromatic aberration is superbly controlled, and I'd highly recommend the lens to anybody who can afford it.

PROS:

  • Among the sharpest 50mm/1.4s available in the market. Super sharp even at f1.4.
  • Practically distortion-free.
  • Fast and silent autofocus.
  • Very versatile, just like Sigma claims: excellent lens for portraiture, and quite suitable for street and studio work.
  • Much cheaper than its only real competitor: the Zeiss Otus 55mm/f1.4

CONS:

  • Sharpness can be a trade-off for hard-edged bokeh elements.
  • Big and heavy.
  • Costs 3 times as much as Canon or Nikon 1.4s
  • Autofocus sometimes fails, shifting focus from the intended focal plane.