Sigma’s recent ART series has primarily been dominated by wide aperture primes along with a few unique, wide aperture zooms. The one exception previously has been the Sigma 24-105mm f/4 OS. The Sigma 12-24mm f/4 DG HSM ART lens take the series to a wider focal length than ever before and is one of the rare lenses in the series without a wide maximum aperture. The 12-24 ART is probably best viewed as Sigma’s answer to the Canon EF 11-24mm f/4L, a monster of a lens that pushed the limits of a rectlinear full frame zoom lens on the wide end. I would be interested in knowing how well that lens has sold, as, frankly, it didn’t incite a whole lot of interest in me. 11mm is an incredibly hard focal length to use well, and I can’t help but wonder how many owners end up taking most of their shots between 15-24mm (ie, the more traditional landscape focal lengths). Apparently Sigma decided the lens needed answering, however, because we have a lens with almost the same focal length (a 1mm loss on the long end). I don’t miss that 1mm one little bit, however, as 12mm is still incredibly wide…wider, frankly, than most shooters will ever need.  Is the Sigma 12-24 ART a lens that should make it into your kit?  Read on to find out.

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Build Quality

The 12-24mm ART is a beautiful albeit large(ish) lens. When you take it out of its square padded case (thanks for that, Sigma!!), you will quickly note that the lens is so wide (particularly towards the front) as to seem almost square rather than cylindrical.  

Its diameter of 4.02”/102mm isn’t far off its length of 5.08”/131.5mm. The unique design makes it seem that the focus ring is on the lens hood, as it is on the flared portion that towards the front of the lens that does include the fixed lens hood. It is perhaps the oddest focus ring I’ve yet encountered, though there is nothing wrong with the action. It moves nicely, though without a particularly big range of focus throw (not uncommon for wide angle lenses).

In this video you can take a closer look at the overall physical dimensions and build of the lens:

The lens is very dense and weighs a hefty 2.54lb (1150 grams). It has a fairly massive lens cap that slips over the fixed lens hood (like other lenses with a bulbous front element).  Unfortunately these caps are a bit of a pain, and I’ve been complaining about them for years.  They don’t fit in a pocket very well and are generally a pain in the field.  The 12-24 ART’s cap does fit securely, however.  

Using traditional screw-in filters are out, though I fully anticipate that third party filter companies like Fotodiox, Formatt Hitech, and Lee Filters will fill those gaps.  Such systems (I use the Fotodiox Wonderpana for the Tamron 15-30 VC) work very well for landscape work but do incur additional bulk and costs.  The physical dimensions of the 12-24 ART are very similar to the chief competitor (the Canon 11-24mm), which is 4.3”/109.22mm x 5.2”/133.8mm and weighs 2.6lb/1180g. Fortunately the Sigma doesn’t copy the Canon’s eye-watering price tag of right under $3000 USD, although the $1599 USD price tag definitely takes the ART series to a new price premium. It will be interesting to see if Sigma loyalists are ready to embrace this new price point.

The lens feels very well made with a feel something like metal (but actually is not). According to Sigma, the lens is constructed from a lightweight and durable thermally-stable composite (engineered plastics) with some internal metal bits, while the lens mount is made from brass. The lens feels just as good (if not better) than most recent Canon L series lenses, though.

Finally! The ART series has some moisture resistance. From Sigma’s press release: “Mount with dust- and splash-proof construction: The lens mount incorporates rubber sealing to protect the mount from dust and water drops. The front and rear lenses feature a water- and oil-repellent coating that is particularly useful when shooting in a drizzle, near ocean spray, and in a wide variety of other conditions. “ While the language here isn’t exactly enthusiastic, it’s a start. I can verify that there is a rubber gasket near the lens mount and also used the lens in some light rain and freezing drizzle without any issues. Those that shoot in more challenging environments, however, will particularly appreciate this new direction for the ART series.

Though not uncommon, I did note that the when the rear element is moved forward there is a fairly significant gap created where I can see into the lens innards. Under normal operational use this shouldn’t be an issue, but if that rear element happened to be forward and the lens was removed (to switch to another lens, for example), it wouldn’t be difficult for dust to get in there.

The zoom ring is fairly close to the barrel and moves nice and smoothly. The lens is internally zooming and focusing. There is only one switch on the lens barrel, and that is a simple on/off switch for the AF (though full time manual override is available with Sigma’s HSM focus motor).

Image Quality

The bottom line for many is in the overall image quality from a lens.  It is fairly large and heavy, moderately expensive, but if the image quality is fantastic many photographers are willing to accept those compromises.  We will examine all the different aspects of the optical performance of the lens.  

One minor caveat.  I had this lens for about 18 days including the last week of November and the first two weeks of December.  The weather was incredibly dreary during that period, so my photos in no way reflect the optimal results that this lens can achieve!

Resolution

If you have a few minutes, I recommend that you watch this video where I interactively look at resolution, chromatic aberration and flare control, vignette, and even coma performance.

I set up a landscape comparison test for the 12-24 ART with two comparison lenses: the Laowa 12mm f/2.8 Zero D that I happened to have for review at the time (which provides a rare comparison at 12mm) and the Tamron SP 15-30mm f/2.8 VC lens that I used to compare the 12-24 ART at the 20mm and 24mm positions. I used mirror lockup, two second delay, and shot at a variety of aperture values. I observed a number of things, including:

12mm Observations

• The 12-24mm is a true 12mm on the long end. It framed basically exactly like the Laowa 12mm.  In fact, if anything, it was a tiny fraction wider (see comparison photo above and note that the left side of the image shows a slight bit wider framing for the Sigma).
• The Sigma was (unsurprisingly to me) sharper than the Laowa with both lenses at f/4. The 12-24 ART has nicely even sharpness across the frame even wide open. This is a very strong f/4 performance at such a critically wide focal length.

• I had previously noted the color rendering of the Laowa in my review of that lens, where I found it had a warm, slight green tint. The Sigma renders much cooler by comparison, but when compared to the Tamron the color rendition is almost identical. The color palette of my introductory video (shot on the 80D with the Canon EF 40mm f/2.8 lens) also matches these lenses. For some reason the Laowa lens consistently produced a different white balance than the other two lenses, but even when equalizing the white balances the Laowa has a very slight greenish cast and is still a bit warmer (see above).
• When stopped down to f/5.6-f/11 the sharpness difference vanishes (the Laowa sharpens up a lot while the Sigma is actually a bit sharper at f/4 than it is at f/8.) The 12-24 ART is clearly optimized to achieve maximum sharpness at about f/5.6. This makes it a good match for high resolution sensors that hit diffraction limits earlier, but may present a challenge if you wanted to stop down further for greater depth of field or to create a nice sunburst effect for bright light points.  Note below the surprising difference between f/4 and f/8.

• The 12-24 ART shows very good chromatic aberration control in this comparison.
• “Draw distance” from the lens is good; it resolved the textures and details in the distant background very well.

The 12mm performance was encouraging.  The lens showed a lot of resolution at f/4, with nicely even sharpness across the frame.  The center won’t always shine compared to other lenses with a lot of sharpness packed into the middle but trailing off towards the edges, but the lens provides nicely consistent sharpness across the frame.  Good color rendition and low CA result in nice real world results.

20mm Observations

• The Sigma faces a much stronger challenger in the Tamron 15-30 VC at 20mm and at wider apertures. The Tamron is a very sharp lens and that is particularly true in the middle of the focus range. They are basically equally sharp wide open with the Tamron at f/2.8 and the Sigma at f/4. The one advantage I can see for the Sigma is that I can see a bit of lateral chromatic aberrations with the Tamron that I don’t see on the Sigma…and those lateral aberrations persist even when the lens is stopped down.

• At f/4 the advantage clearly shifts to the Tamron. At equivalent settings the Tamron is delivering a brighter image overall plus has next to no observable vignette for field use. It is clearly sharper and with greater contrast in the center of the frame, though the advantage is very slight at the edges (the Sigma’s sharpness is still very even). There is still some CA at the edges of the frame that the Sigma doesn’t have.
• At f/5.6 the Sigma has gained a small edge on the edges of the frame while the Tamron rules the center 2/3rds of the frame with higher resolution and contrast. A slight bit of the fringing from the Tamron persists in the extreme edges.
• At f/8 the Tamron is still has the resolution edge, but the Sigma has a slightly more pleasing performance at the edges of the frame (without correction) because a bit of fringing persists with the Tamron.  It is worth noting that the Sigma behaves more traditionally from around 16mm on with peak sharpness coming at smaller apertures like f/8.
• I slightly prefer the color rendering from the Tamron. It is a bit cooler but I also find the overall contrast and color saturation a little stronger from it.

Here’s a quick look at some crops from the center and edges of the frame along with the full 20mm image.

24mm Observations

• The Sigma showed well on the wide end by having a true 12mm focal length when compared to a 12mm prime. It isn’t quite as convincing at 24mm. Both lenses record 24mm in the EXIF data, but the Sigma is framing a little more loosely. 23mm, maybe? This is pretty common for lens makers; they tend to round up or down to the more common focal lengths. No one wants to buy a 11.9-23.1mm zoom!  In the photo below you can that there is a whole tree in the frame that isn’t there on the Tamron (which also reads 24mm in the EXIF data).

• Comparing sharpness with both lenses wide open shows neither delivering a convincing performance in the corners. The Sigma is bit better across the frame at f/4 than the Tamron is at f/2.8.
• The situation strongly reverses with the Tamron stopped down to f/4. It has noticeably better sharpness and contrast throughout all but the very edges of the frame. Extreme edge performance is a strength for the Sigma.
• Similarly at f/5.6 the Tamron has a clear advantage for about 90% of the frame, but the Sigma rules the last 10% at the edges of the frame. This trend continues through f/8, though the Tamron is finally looking sharp in the corners now and Sigma’s lead there is marginal.

My resolution conclusion after looking at a lot of pictures over my review is that while the Sigma isn’t a record breaker in the center or mid portion of the frame, it does manage to provide very even consistency across the frame. It holds up well for the most part when compared to the very good Tamron 15-30 VC, which itself covers a less extreme focal length. I wasn’t blown away by the absolute sharpness from the lens but was certainly impressed with the consistency with which it delivers that sharpness.  It is worth noting that if you are shooting with a very high megapixel body (where diffraction sets in early) you will be able to get peak sharpness from the lens at f/5.6 (beneath the diffraction limit of any current camera as of 2016)…at least at wide apertures. The tradeoff is that if you want to focus down further to increase depth of field you may find a minor sharpness penalty at smaller apertures.  I did find that peak sharpness figures at 18-24mm came at more traditional small apertures like f/8.

Other Image Quality Observations

The vignette at f/4 is noticeable though less extreme than some of the recent lenses I’ve seen (Zeiss Milvus 18mm f/2.8 and Canon 16-35mm f/2.8L III). I’d say it is right under three stops in the extreme corners. I was able to clear it up completely with a moderate +45 strength and moving the midpoint to a 25 value in Lightroom (no automatic profile exists yet for the lens). It isn’t as good as the Tamron 15-30 VC (the best lens I’ve seen for this), but this a pretty decent performance for going so wide.

I’ve been dealing with a lot of grey weather during my review period (I wish all lenses were released in spring, summer, and fall!!), so I grabbed a brief window when the sun was brightly shining to test the flare resistance of the lens. Curved front elements like all lenses this wide have can sometimes catch some stray rays of light and create ghosts. The Sigma does a pretty good job with the sun shining into that huge front element. Contrast remains very good, and, while I got a bit of prismatic haze right in the epicenter of the sun in the frame, the image looks very good. I was able to induce a small amount of green ghosts, but they were small and relatively unobtrusive. Flare resistance is better on the 12mm end than the 24mm, though neither is bad. At 24mm there is a bit of veiling that I don’t see at 24mm.

With the aperture closed down to f/11 the lens produced a nice sunburst/sunstar. It is better defined at the wide end than the telephoto end.  This isn’t quite as strong a flare resistance performance as the recent Canon 16-35L III (which has the advantage of a flat front element), but I was pleased with the overall result.

As already noted, chromatic aberrations are very well controlled. I didn’t really see anything for my use that I would consider needing of correction.

Coma Performance

The weather was anything but accommodating during my time with the 12-24 ART. I use an app for my iPhone called SkyLive that helps determine optimal conditions for shooting astrophotography. I saw mostly ratings of 0-10% (out of 100)! Overcast, snowstorms, and generally a very low cloud ceiling night after night. I had pretty much despaired. Sigma Canada was nice enough to offer me an extra weekend just in case with the lens, and on my second to last night with the lens I caught the closest thing to a break that I was going to get. My app said conditions were 34%. Still rated “Poor”, and typically not a night I’d even bother with, but the next night was back to a 6% rating. You take what you can get.

It was the coldest night thus far of the new winter, and my car said the temperature was a chilly -15C where I set up. The things we do for photography…

The biggest challenge on this particular night was extremely bright moonlight that makes it harder to get good “pop” on the stars, but the results weren’t bad.

More importantly I was able to get a get a good read on the coma performance…and what I saw was really pretty decent. f/4 is not a fantastic aperture for typical astrophotography, but on a brighter night it wasn’t a huge impediment. The high, even sharpness of the lens produced nice, crisp star points. Some of the brightest points towards the edges did become a little wedge shaped, but not strongly “winged”. At 12mm, however, each star point fills such a small amount of the frame that any existing coma can only be slightly seen at pixel level.

I compared it with the Tamron 15-30 VC (a very good astrophotography lens). The lens would still be my favorite due to a larger maximum aperture and less vignette, but in terms of the actual comatic aberrations there isn’t a big difference between the two.

So, while I wouldn’t personally choose a lens with a maximum aperture of f/4 primarily for astrophotography, I see no reason with this lens couldn’t be used for this purpose. Viewed “globally” the end results are quite nice.

Distortion Results:

I did a direct distortion comparison with the Laowa 12mm f/2.8 Zero D lens.  The “Zero D” stands for Zero Distortion, so unsurprisingly the Laowa is a very strong performer when it comes to having extremely low levels of actual distortion (see my review here). The Laowa is the better performer, but the difference is surprisingly marginal.

In head to head comparisons I found the differences in barrel distortion to be subtle at best, which means that the 12-24 ART is definitely ahead of the new Canon 16-35mm f/2.8L III or the Tamron SP 15-30mm f/2.8 VC in this regard. Even without correction (there is no profile for this lens yet) I see little to object to in field use.

It is key to understand that any wide angle lens will produce a keystone (perspective distortion) if the sensor is angled in relation to the subject. If you tilt the camera and compose with your subject close the frame you can get some very weird results (see this lovely portrait below).

This isn’t the same as barrel distortion, however, and can be managed by the way that you compose. If the sensor (camera) is level with the subject you should get nice results with this lens.

I shot a small bathroom to see how the lens would work in architectural situations. The advantage to the Sigma is that as a zoom you have different framing options. 12mm is really, really wide, and in very small spaces (like this bathroom), having a very wide framing is advantageous because it allows you to fit the whole room in. In bigger spaces you might really lose a sense of the details by being so far “removed” from them, so zooming in and framing a little tighter is a nice option.

With minimal distortion and negligible CA the only place I’m really missing a corrective profile is for vignette. There are few optical flaws with the lens.

As always, I recommend that you take a look at the image gallery here to see more real world results.

Autofocus

Autofocus is always a point of close attention for me when reviewing any lens, but particularly Sigma lenses due to having had a number of issues with focus inconsistency during previous reviews.  Sigma has touted revised HSM motors with one third more torque in both this lens and the 85mm f/1.4 ART, which I had better focus success with than any ART lens previously (particularly with using the center group).  Now, to be fair, a lens like the 12-24 ART has very, very little stress on autofocus accuracy.  Its whole focal range is either extremely wide or moderately wide (12-24mm).  Then there is the smallish maximum aperture of f/4, so if you are focusing at a distance of 10 feet the depth of field is already infinite from 2.82 feet to infinity.  In other words, it is very easy for everything to be in focus all the time, and that is pretty much what my experience has been.

You can focus down closely to 9.45″/24cm and have pretty decent reproduction ratio of 0.20x.  

You can even create a little bokeh with the lens, but the situations will be fairly rare for this.

Some reviewers have reported an issue with focus shift (cameras focus with the lens wide open and then stop down to the preset aperture when the shutter closes). In most cases accurate focus at the more demanding maximum aperture equals accurate focus at smaller apertures.  But in some lenses there is an aberration where wide open focus does not equal correct focus at other apertures (the focus shifts).  The end result is that everything should be in focus, but isn’t.  It would take a major amount of focus shift to be evident in the real world with a lens like this, and I personally did not really witness that.  Yes, I had a few images that I thought should be in focus but weren’t, but it didn’t happen often enough for me to observe a pattern of poor behavior… and you always have a few misfires in the real world when you shoot a lot in varying conditions. 

I can’t account for what other reviewers encountered (and this may be more of an issue when shooting charts than in the real world due to the deep depth of field in most situations with the lens), so I’m not going to criticize something that I didn’t actually observe myself.  I bring it up more to say that you might want to watch for this with your own copy, and if it isn’t an issue…just enjoy the lens.  Although I am a reviewer and people seek my opinion, I often tell people that the most important opinion is their own.  Don’t lose sleep over an issue that someone else might have experienced if you are not!

Autofocus was quick, quiet, and, for the most part, accurate.  Enough said.

Conclusion

Overall the Sigma 12-24mm f/4 DG HSM ART is a very competent lens. It has few major flaws. Chromatic aberrations are well controlled, distortion is low, and vignette, while clearly present at f/4, isn’t quite as bad as some of the recent releases from other major companies.  It does a very credible job when shooting the night sky, though having a relatively small maximum aperture puts it at a bit of disadvantage. It is a legitimate 12mm on the wide end, putting it in rare company.

It falls a little short of a true 24mm, but that isn’t unusual, and I would argue that the true 12mm on the wide end is ultimately more important. It isn’t as absolutely sharp at equivalent apertures and focal lengths as the new Canon 16-35mm f/2.8L III or the Tamron 15-30mm f/2.8 VC, but those lenses have the advantage of being able to stop down a full stop before the comparison begins. One thing to note, however, is that the 12-24 ART is optimized for f/4-5.6 performance (at least on the wide end of the focal range) and I actually saw a trend where the image quality tended to be a bit worse rather than better as the lens was stopped down. There is finally some weather resistance included in the build. It is a big, heavy lens, however, and sets a new price ceiling for the ART series lenses.  It has a maximum aperture of f/4 (that will cool the interest of some for it as an astrophotography lens) and is unable to use traditional filters. It obviously undercuts the chief competitor from Canon (the 11-24mm f/4L) by a large margin, however. I think the bigger question will be how many people feel that they need a lens that goes that wide, and if having the wider focal length is worth the additional challenges that come with it.  If you are an interior shooter, architectural photographer, or a landscape photographer who wants to capture scenes with a wider focal length than the standard wide angle zooms allow, however, the Sigma 12-24 ART should definitely be a lens that you take a long look at.

 Pros:

• Very low distortion
• A true 12mm on the wide end
• Very even resolution across the frame even at wide apertures
• Very good coma performance
• Extremely low chromatic aberrations
• Nice build which now includes some weather resistance
• Good flare resistance
• Includes nice padded case

Cons

• Sets a new high in price for an ART series lens
• Can’t use traditional filters
• Some competitors sharper in the center of the frame
• Bulky and heavy
• Not quite a full 24mm on the long end
• Some shooters and reviewers have reported focus shift issues

 Thanks to Sigma Canada for providing me a loaner copy of the 12-24 ART for review!

Gear Used:
Canon EOS 5D Mark IV (5D4)
Canon EOS 6D DSLR Camera (Body Only)

Sigma 12-24mm f/4 DG HSM ART | B&H Photo
Sigma 12-24mm f/4 ART | Amazon USA
Sigma 12-24mm f/4 DG HSM ART from Simon’s Camera in Canada (Use code SIGDLA for special gift with purchase)
Sigma 12-24 f/4 ART | Amazon Canada
Adobe Lightroom CC Software for Mac and Windows (Boxed Version)
Adobe Photoshop Creative Cloud 1-Year Subscription
Alien Skin Exposure X (Use Code “dustinabbott” to get 10% anything and everything)

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Alternatives:

I’ve recently also reviewed a very different way to get to 12mm – the Laowa 12mm f/2.8 Zero D lens.  Which would work better for you?  Check out this video where I look at the pros and cons of each lens.