Sigma 12-24mm f/4 DG HSM Art Lens Review

One way to create differentiating photographs is to use an extreme lens. The ultra-wide angle Sigma 12-24mm f/4 DG HSM Art Lens fits that definition, providing extreme wide angles of view rivaled by few other rectilinear (non-fisheye) lenses. These wide angles of view take in vast scenes and can provide a unique perspective on the world, especially with a close subject.

With this lens, Sigma brings us their third version of a 12-24mm DG (full frame) HSM lens and their first within the Global Vision Series. The Sigma 12-24mm f/4.5-5.6 DG II HSM Lens replaced its predecessor, the 12-24mm f/4.5-5.6 EX DG HSM Lens (just missing the "II"), but that is not likely the case with the Art lens introduction. As of review time, both the II and Art lenses remain in production and a life expectancy for "II" was "not available". Though these lenses share the same focal length range, they are quite different in other regards including max aperture, size, weight and price. They will may remain stablemates for at least some period of time into the future.

When I reviewed this lens's predecessor, the "II", I stated "No other full frame compatible lens offers a rectilinear focal length this wide." Since that time, Canon unleashed the very-impressive (and expensive) EF 11-24mm f/4L USM Lens and a proper revision to that sentence would now say "Only one other full frame compatible lens offers a rectilinear focal length wider than this lens aside from the other Sigma option." However, even though the Canon's 1mm wider focal length makes a noticeable difference, 12mm remains incredibly wide and the difference between it and the more ubiquitous 16mm wide-angle focal length is substantial.

In addition to the extreme 12mm focal length, this lens offers a full range of also useful focal lengths reaching up to the far more common 24mm. All this in a beautifully-designed package that delivers good image quality for a mid-tier price.

Focal Length Range

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I always start my lens selection process with the preferred focal length or focal length range and indeed this lens is special in this regard. You likely have no substitue for this lens's capability in your kit. And, if you've never used focal lengths this wide, you are in for a LOT of fun!

There are wider angle full frame fisheye lenses available, but these lenses capture a barrel-distorted image with straight lines rendered curved (unless they pass directly through the center of the frame). There are wider angle APS-C lenses available, but these have a much smaller image circle producing a much narrower angle of view and are essentially incompatible with full frame cameras. Aside from the Canon 11-24 L, the widest rectilinear focal length available in a full frame DSLR lens is found in this lens's predecessor and the next widest option is found in Canon's EF 14mm f/2.8L II USM Lens, Nikon's 14-24mm f/2.8G AF-S Lens and the Samyang/Rokinon/Bower 14mm f/2.8 IF ED UMC Lens.

The 14mm angle of view is wide. But, 12mm is noticeably wider than 14mm (122° vs. 114°). The wider the focal length, the more significant each mm of difference makes and when you get this wide, each mm is significant. The difference between 12mm and 15mm (122° vs. 110°) or 16mm (122° vs.108° 10') is even more considerable. If 24mm is the widest angle in your kit, 12mm is going to blow you away.

Seeing that difference with you own eyes will convey the story best. I spent most of a day photographing the Pennsylvania Capitol building with this lens. Here is a focal length comparison captured in the senate chamber.

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Compare the widest focal length currently in your kit with 12mm to see what you are missing.

The Sigma 12-24 is far less exciting from a focal length perspective when placed in front of an APS-C/1.5x or 1.6x FOVCF sensor format camera where it provides a 19-38mm full frame-equivalent angle of view on an APS-C sensor camera. Far less exciting in terms of angle of view realized and far less exciting because there are many APS-C zoom lenses with 12mm and even wider focal lengths available. But, there remains some merit in creating a full frame-compatible lens kit behind an APS-C body: planning for a future full frame upgrade.

What the Sigma 12-24 offers to full frame DSLR owners is, as illustrated above, a stand-out ultra-wide angle of view. Working with angles of view this wide is fun, and the results can differentiate your images from those of everyone else (unless they have this lens of course). As I said about the predecessor lens, you might want to wear scene-complementing shoes when working with this lens at 12mm. Keeping your own shadow from contaminating the scene is another challenge (consider wearing a nice hat and embracing the selfie aspect).

Extreme wide angles can differentiate your work from the crowd, but creating compelling extreme wide angle compositions remains a challenge. It is easy to go out and simply shoot at ultra-wide focal lengths, but ... these snapshots will, more often than not, look like ... snapshots. An ultra-wide angle of view pushes the background away, making it much smaller in the frame relative to close foreground subjects. Ideal compositions will incorporate an interesting, close foreground subject along with a complementary/supporting midground and background in the scene.

Unless working in a tight space, there is going to be a lot of background in the scene and keeping the entire background attractive becomes challenging in many locations. The big landscape of the American Southwest is an example of a great location to take this lens to, but there are certainly applications close to everyone's home. Of course, the 24mm focal length is not extreme and is quite easy to compose with, providing the ideal angle of view for many uses.

As you likely already determined, these focal lengths are popular with landscape photographers. While considering this lens for landscape photography use, a detracting attribute must be understood and that is the beautiful bulbous front lens element that precludes the use of standard threaded front filters, namely circular polarizer and neutral density filters. Companies such as Fotodiox implement filter solutions for these types of lenses, but the filter holder and the filters themselves are quite large. It should also be noted that a slip-in rear gel filter holder, useful for holding neutral density gel filters, is not provided. Regardless, there remains a lot of landscape photography to be done without filters.

There are of course many other photography subjects to be captured with the 12-24mm focal length. With this lens, wedding photographers will be able to capture the big picture. Architecture photographers will find this lens useful with its ability to capture large structures and real estate photographers will especially find this lens valuable in making their properties appear large. This lens will make a great option for attaching to a remote camera at sporting events, capturing the start and/or finish of a race, covering the goal, mounted over the basket, etc. It will also capture the big image of the arena and will work for the overhead shot of the MVP sports figure being mobbed for interviews after a big game.

There are many additional needs for wide angle photos captured in tight spaces including vehicle interiors and large groups. Understand that when people are in the photo, care will be required to prevent perspective distortion. Noses and heads can easily be made to appear larger than the rest of the body parts (ears, feet, etc.) and far larger than other subjects in the composition. However, this focal length range can work well for environmental portraits, showing people in their places.

The 12-24 range can be interesting when used for video.

Here is another focal length range illustration from the PA State Capital Rotunda. Note that the stairs are curved – you are not looking at severe linear distortion.

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As I noted, this lens has a really fun focal length range to photograph with and this building is full of subject matter.

Max Aperture

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Wide apertures are often desirable for creating shallow depth of field, but what wide angles are not best at is creating diffusely-blurred backgrounds. The out-of-focus details in the background are not enlarged enough for a strong blur to be created by the ultra-wide angles of view.

Wide apertures are also desireable for the light they allow to reach the sensor, permitting shorter shutter speeds and/or lower ISO settings, but wide angles tend to render subjects small in the frame. Small in the frame means that subjects do not cross sensor pixels as fast, meaning that longer shutter speeds may be adequate for capturing sharp images, negating some of the need for wider apertures.

The f/4 max aperture is moderately wide. However, the f/4 max aperture, available over the entire focal length range, is a nice feature upgrade from Sigma's last 12-24mm lens. That was an f/4.5-5.6 lens, but the f/4.5 aperture was only available at 12mm, so it was mostly an f/5.0-5.6 lens. I like that the Art lens's has a wider aperture and especially like that wide open exposure settings can be maintained over the full focal length range.

It would have been great to see Sigma take this lens out to f/2.8 as this focal length range is great for night sky photography. But, this already somewhat heavy lens would have taken on considerably more weight and I'm sure there would have been a significant price penalty in addition. Otherwise, I do not encounter many situations where an f/4 aperture is inadequate in this focal length range (and nightscapes can be captured at f/4 at ultra-wide angles).

If f/4 is not enough for your scenario (especially indoors), adding your own light to the scene is an option. Keep in mind that, even with the flip-down diffusor in place, most flashes will not cover angles wider than 14mm. Many accessory flash modifiers are available to cover the wider-than-14mm angles. This diffusion of course reduces the flash's effective power level and distance.

Image Quality

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From the always-important image sharpness perspective, this lens is a good performer with a caveat that I will of course explain. At f/4, this lens is quite sharp in the center of the frame over the full focal length range aside from performance becoming modestly softer from 20mm through 24mm. Stopping down to f/5.6 brings sharp center of the frame results to the entire focal length range.

At 12mm, the mid frame is slightly soft and the corners, though not terrible, show stronger issues. By 14mm, the corner issues are resolving and results are looking good even at f/4. From 16mm onward, f/4 corner performance slowly degrades until results are soft even in the mid-frame at 24mm f/4. Stopping down to f/5.6 brings about a noticeable improvement in the corners, bring all but those from the longest focal lengths up to impressive in performance. The longer focal length corners respond better with another stop of aperture closing.

Overall, and especially for a lens with such wide angles, this lens delivers impressive sharpness. I didn't have image quality results from this lens prior to spending the day at the capitol building. So, I was taking a chance and watching the results closely. As is often the case when photographing architecture, I wanted everything in focus and f/8 was delivering both the depth of field and the sharp corners I wanted. I was quite impressed when reviewing my results on the back of the camera.

I mentioned the caveat. What I didn't notice during this shoot was focus shift. As this lens is stopped down, the plane of sharp focus shifts farther away. Because Canon cameras focus with a wide open aperture, this change is not accounted for during either viewfinder or Live View-based focusing (AF or MF). Stopped down manual focusing in Live View will account for the change, but ... this is not how we typically focus.

Fortunately, nearly all of my images from this day had good sharpness regardless. But, knowing how this lens behaves is helpful.

Let's look at some 100% resolution crop samples taken from the center of the frame. These images were captured in RAW format using a Canon EOS 5Ds R and processed in DPP (Digital Photo Professional) using the Standard Picture Style with sharpness set to "1".

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In the f/4 images, find the sharpest details, indicating the center of the plane of sharp focus. Then, watch what happens when the narrower apertures examples are selected (mouseover or click/tap on the labels). The distant details snap into sharp focus and the foreground details become slightly more blurred. That is not what you want to happen, but ... the effect can be accounted for if understood. Basically, you will usually want to focus a certain distance in front of the subject/scene when shooting at an aperture narrower than f/4. Overall, what is in focus is quite sharp.

Now, let's move to the corners. The capture and processing specifics for the results below are the same as for those above except that the crop was taken from the absolute top left corner of the frame.

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While you do not see perfection here at f/4, this performance is quite good for an ultra-wide angle lens. Stop down to f/5.6 and the corners are quite impressive and they are even more so at f/8. Notice the subject framing shift slightly in some of these images? While it is possible that I moved the camera slightly while changing the aperture, it happened frequently enough for me to believe that this may be caused by the aperture being stopped down. Perhaps a little focus breathing is taking place?

Obvious in the corner comparisons is that some peripheral shading clears as the aperture is stopped down. At f/4, the 12mm corners have over 2.5 stops of shading. This is a comparably low amount, but enough to show in images (and this effect may even be welcomed at times for drawing the viewer's eyes toward the center of the frame). The amount of shading quickly decreases to roughly 1.7 stops as the lens is zoomed to 16mm. This approximate amount of shading holds throughout most of the balance of the focal length range until 24mm where slightly more shading is seen (close to 2 stops).

Stopping down a full stop to f/5.6 does not make the significant impact in regards to vignetting reduction that we often see. At f/5.6, about 2 stops of shading remains at 12mm and roughly 1.2 stops remain throughout the balance of the focal lengths. At f/8, shading ranges from about 1.4 stops at 12mm down to 0.8 stops at 24mm. The rule of thumb often used is that less than 1 stop of vignetting will not be noticed in a majority of images. At f/8, that line is crossed at about 20mm. In regards to vignetting, there is essentially no gain realized by stopping down to f/11.

CA (Chromatic Aberration) is another image quality detractor worth looking at. The most easily recognized type of CA is lateral (or transverse) CA. Lateral CA shows as various wavelengths of light being magnified differently with the effect being increasingly noticeable toward the image circle periphery, causing the most-effected area of the image to appear less sharp due to misaligned colors. Look for the strongest color fringing along edges of strongly contrasting lines running tangential (meridional, right angles to radii) near the corners of the frame, generally irrespective of the aperture used.

LatCA is normal in a zoom lens and the question usually is how much impact is there with the two ends of the focal length range generally suffering the most. Fortunately, lateral CA is easily software corrected by radially shifting the colors to coincide. Especially fortunate is that latCA is quite mild over this lens's entire focal length with a small amount becoming visible by the 24mm end.

Following are three 100% EOS 5Ds R crops taken from the absolute top right corner of the frame.

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Especially for such wide angle focal lengths in a zoom lens, these results look great.

Here is a series of 100% center-of-the-frame crops showing focus in front (F) and back (B) of the subject.

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While there is a slight difference in fringing colors of the blurred highlights in each comparison, the difference is not big and the fringing is not strong. Stopping down removes what there is. Axial (bokeh) CA appears well controlled and the center of the frame is not being strongly impacted by spherical aberration.

Even with the sun in the corner of the frame, this lens shows few flare effects at f/4. Flare effects generally become more obvious as the aperture narrows and while this lens is not flare-free at narrow apertures, it continues to perform quite well in this regard.

Looking at how stars are rendered in the corner of the frame can tell us something in regards to image quality. Revealing coma is one goal. Coma is generally recognized by sharp detail contrast towards the center of an image and long, soft contrast transition toward the image periphery. Coma is most visible in wide aperture corners and significantly resolves when the lens is stopped down. Here are samples taken from close to the top right corner of a 5Ds R frame (no tracking mount was used).

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Wider angle lenses create smaller stars that tend to look better in this test, but overall, these results are decent.

It is an extreme-ultra-wide angle zoom lens, so it has a lot of linear distortion, right? Not necessarily. This lens does have barrel distortion at 12mm, but the amount is only mild. The distortion profile transitions to a negligible amount at 16mm. By 20mm, a slight amount of pincushion distortion is present and slightly more is dialed in by 24mm. The site's distortion comparison tool is a great place to see and compare this lens attribute, but I direct your attention to the top of the frame in the uncropped/reduced real world samples shared below.

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As already discussed, this lens is not capable of creating a strongly-blurred background, but there remains some value in good blur quality or bokeh. And, in that regard, this lens has been performing well. In general use, the strongest background blur will be created at 24mm with a close subject and distant background. Here is a look at the specular highlights created by that scenario (f/8 at 24mm).

A 9-blade aperture is responsible for the roundness of the out of focus specular highlights. With a narrow aperture selected, the blades also create 18-point stars from point light sources as seen below.

While this lens takes a hit for its focus shift attribute, it delivers good image quality performance overall.

Focusing

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The 12-24mm Art Lens gets Sigma's best AF system, called HSM (Hypersonic Motor). At normal focus distance changes, AF locks on the subject nearly instantly. Do a full extent AF adjustment, from near minimum focus distance to infinity or vice versa, and you can easily watch the lens make its adjustment. Quiet focusing is normal for HSM systems and this one again meets that expectation, though it is slightly louder than some recently-introduced lenses.

Angles of view this wide typically result in lots of depth of field and AF systems are not stressed to keep a subject within that depth of field. Regardless, AF accuracy from this lens has been quite good for me and focus calibration can be adjusted (in detail) using the Sigma Dock (more later). As noted and demonstrated earlier in the review, focus shift is an issue and calibration via the dock will not resolve this one (though calibration for a specific aperture may be possible).

As usual for Sigma HSM implementations, internal focusing is featured and FTM (Full Time Manual) focusing is enabled. Both are nice features commonly found on quality lenses.

The 12-24's effective focal length changes modestly with focusing, causing subjects to change size slightly as the focus ring is turned. The review copy of this lens requires a focus adjustment change after changing focal lengths (it is not parfocal), but depth of field can easily cover the change in many instances.

The 12-24 Art's manual focus ring is nice – smooth with no play and with an ideal amount of rotation for precise manual focusing even with close subjects. The location of this ring, positioned on the rear of the wide portion of the front of the lens, is a bit unusual. The focus ring is somewhat narrow and inherently quite wide in diameter. With only the rubber ribs slightly raised above the barrel, the ring is well protected from inadvertent focus changes though quite usable.

A great trend currently being seen in lens design is shortened MFD (Minimum Focus Distance) with increased MM (Maximum Magnification) and the Sigma 12-24mm f/4 DG HSM Art Lens adds its name to this list. The 12-24 Art's MFD has been shortened to 9.4" (240mm) from 11.0" (280mm) and the MM increases modestly to 0.20x from 0.17x. The 0.20x spec is best-available for lenses wider than 16mm, though the spec is only mediocre in the entire field of lenses. Here is a table showing a large array of wide angle lenses:

Model	Min Focus Distance "(mm)		Max Magnification
Canon EF 8-15mm f/4 L USM Fisheye Lens	5.9	(150)	0.39x
Canon EF-S 10-18mm f/4.5-5.6 IS STM Lens	8.7	(220)	0.15x
Canon EF-S 10-22mm f/3.5-4.5 USM Lens	9.4	(240)	0.17x
Canon EF 11-24mm f/4L USM Lens	11.0	(280)	0.16x
Sigma 12-24mm f/4 DG HSM Art Lens	9.4	(240)	0.20x
Sigma 12-24mm f/4.5-5.6 DG II HSM Lens	11.0	(280)	0.17x
Sigma 12-24mm f/4.5-5.6 EX DG HSM Lens	11.0	(280)
Canon EF 14mm f/2.8 L II USM Lens	7.9	(200)	0.15x
Nikon 14mm f/2.8D AF Lens	7.9	(201)	0.15x
Nikon 14-24mm f/2.8G AF-S Lens	11.0	(280)	0.15x
Sigma 14-24mm f/2.8 DG HSM Art Lens	10.2	(260)	0.19x
Zeiss 15mm f/2.8 Milvus Lens	9.8	(250)	0.11x
Tamron 15-30mm f/2.8 Di VC USD Lens	11.0	(280)	0.20x
Canon EF 16-35mm f/2.8L III USM Lens	11.0	(280)	0.25x
Canon EF 16-35mm f/4 L IS USM Lens	11.0	(280)	0.23x
Nikon 16-35mm f/4G AF-S VR Lens	11.4	(290)	0.25x

While 0.20x is not near record setting, combined with the 12mm focal length, the lens is able to create a strong perspective.

To reduce the MFD and thereby increase the MM, mounting an extension tube behind the lens is generally a good option. But, not with this lens. With a short 12mm Extension Tube II installed, this lens has a maximum focus distance just beyond the end of the non-removable hood. Lighting within this area becomes a real problem and the corners of the frame are visibly blurry even in the viewfinder.

Build Quality & Features

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With the Global Vision series, Sigma introduced a modern, classy-looking, tightly-dimensioned, high-quality design for their lenses. These lenses feel as great as they look, increasing their fun-to-use factor. While the Sigma 12-24mm f/4 DG HSM Art Lens, with the large convex objective lens, has a somewhat unique shape, it definitely looks like a member of the Global Vision family.

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While this lens does not change external dimensions when zoomed, the objective lens does move in/out within the permanently affixed hood. The zoom ring is easy to find and, with the focus ring riding on the broad part of the lens, it is not easy to confuse the two rings. The only other moving exterior part is the manual/auto focus switch nicely positioned on a slightly raised switchbank. As standard with Global Vision lenses, the back of the switch shows white when in the auto position.

This lens has some weather sealing, including a rear gasket seal as seen below.

Increase the aperture by 2/3 to a full stop and the lens elements are going to be significantly larger. Lens elements are not light, so increasing the size of the lens elements is going to be noticed on the scales. And, as you would expect, the 12-24 Art weighs in at a noticeably-heavier weight than the 12-24 II, though it does not quite catch the Canon 11-24.

Model	Weight oz(g)		Dimensions w/o Hood "(mm)		Filter	Year
Canon EF 8-15mm f/4 L USM Fisheye Lens	19.1	(540)	3.1 x 3.3	(78.5 x 83.0)	n/a	2010
Canon EF-S 10-18mm f/4.5-5.6 IS STM Lens	8.5	(240)	2.9 x 2.8	(74.6 x 72.0)	67mm	2014
Canon EF-S 10-22mm f/3.5-4.5 USM Lens	13.6	(385)	3.3 x 3.5	(84.0 x 90.0)	77mm	2004
Canon EF 11-24mm f/4L USM Lens	41.6	(1180)	4.3 x 5.2	(108.0 x 132.0)	n/a	2015
Sigma 12-24mm f/4 DG HSM Art Lens	40.6	(1150)	4.0 x 5.2	(102.0 x 131.5)	n/a	2016
Sigma 12-24mm f/4.5-5.6 DG II HSM Lens	23.7	(670)	3.3 x 4.7	(83.8 x 119.4)	n/a	2011
Canon EF 14mm f/2.8 L II USM Lens	22.8	(645)	3.1 x 3.7	(80.0 x 94.0)	n/a	2007
Nikon 14mm f/2.8D AF Lens	23.7	(670)	3.4 x 3.4	(87.0 x 86.5)	n/a	2000
Nikon 14-24mm f/2.8G AF-S Lens	34.2	(969)	3.9 x 5.2	(98.0 x 131.5)	n/a	2007
Sigma 14-24mm f/2.8 DG HSM Art Lens	40.6	(1150)	3.8 x 5.3	(96.4 x 135.1)	n/a	2018
Zeiss 15mm f/2.8 Milvus Lens	33.4	(947)	4.0 x 3.9	(102.3 x 100.2)	95mm	2016
Tamron 15-30mm f/2.8 Di VC USD Lens	38.8	(1100)	3.9 x 5.7	(98.4 x 145.0)	n/a	2014
Canon EF 16-35mm f/2.8L III USM Lens	27.9	(790)	3.5 x 5.0	(88.5 x 127.5)	82mm	2016
Canon EF 16-35mm f/4 L IS USM Lens	21.7	(615)	3.3 x 4.4	(82.6 x 112.8)	77mm	2014
Nikon 16-35mm f/4G AF-S VR Lens	24.0	(680)	3.2 x 4.9	(82.5 x 125.0)	77mm	2010

For many more comparisons, review the complete Sigma 12-24mm f/4 DG HSM Art Lens Specifications using the site's Lens Spec tool.

The weight of this lens is noticeable when carried for long periods of time, but not burdensomely so. The size of this lens has also increased from the II, but it remains in line with other popular lenses.

Positioned above from left to right are the following lenses:

Canon EF 8-15mm f/4 L USM Fisheye Lens
Nikon 14-24mm f/2.8G AF-S Lens
Sigma 12-24mm f/4 DG HSM Art Lens
Canon EF 11-24mm f/4L USM Lens
Tamron 15-30mm f/2.8 Di VC USD Lens

Use the site's product image comparison tool to visually compare the Sigma 12-24mm f/4 DG HSM Art Lens to other lenses.

As already noted, this lens is not compatible with standard threaded front filters and no provision is made for use of a rear drop-in gel filter. Those wanting to use circular polarizer and neutral density filters will need to make use of a third party filter holder and large filters.

Commonly provided with lenses having integrated hoods is a lens cap that also covers the sides of the hood and that lens cap style is provided with the 12-24 Art lens. This cap uses a friction fit via a thin ring of flocking-like material inside the hood. While staying attached is problematic for some of these caps, this one has been holding on nicely.

The Sigma 12-24mm f/4 DG HSM Art Lens arrives in a nice zippered padded nylon case with a shoulder strap, though without a belt loop.

Sigma Global Vision and the USB Dock

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Sigma's Global Vision lenses get a classification of "A", "C" or "S", representing a primary Sigma-intended use of "Artistic", "Contemporary" and "Sports". A full description of these categories can be found in the Sigma 35mm f/1.4 Art Lens press release.

Sigma has been introducing some nice lenses in the Global Vision series, but I have never been a fan of the narrow categorization structure. This of course is an "Art" lens and as such, gets an "A" stamped in a classy chrome circle on the lens barrel. Don't limit the lens's use to its letter designation.

A great feature of the Global Vision lenses is compatibility with the Sigma Dock. The dock, working in conjunction with the Sigma Optimization Pro software, allows the lens's firmware to be updated (bug fixes, compatibility updates, feature enhancements, etc.) and allows precise autofocus calibration at four distances. FTM can also be disabled/controlled via the dock. Here are some screen grabs showing some of the functionality.

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The focus calibration values were set for illustration purposes only.

Price, Value, Compatibility

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This is a moderately expensive lens, but if compared to the closest non-Sigma alternative, the Canon 11-24, it is a bargain.

The Sigma 12-24mm f/4 DG HSM Art Lens is available in Canon (reviewed), Nikon, Sony/Minolta and Sigma mounts and qualifies for Sigma's Mount Conversion Service in case you change your mind. My standard disclaimer: There are potential issues with third party lenses. Since Sigma reverse engineers (vs. licenses) manufacturer electronics and algorithms, there is always the possibility that a DSLR body might not support a (likely older) third party lens. Usually a lens can be made compatible by the manufacturer via a firmware update, but this cannot be guaranteed. There is also the risk of a problem that results in the lens and body manufacturers directing blame at each other. Compatibility with the Sigma USB Dock is risk reducing as Sigma can release firmware updates for dock-compatible lenses. Sigma USA's 4-year warranty is superior to Canon's standard 1 year warranty (Sigma's international warranty is also 1 year).

The reviewed lens was sourced online/retail.

Alternatives

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As discussed early in this review, the 12-24 has few direct competitors, at least few that go as wide as 12mm. The primary non-Sigma competitor is the Canon EF 11-24mm f/4L USM Lens and this was the lens I was anxious to put the Sigma up against. Would the Canon be worth the over-40% price premium?

From an image sharpness perspective, the Canon bests the sigma. The Canon wins all comparisons at f/4 and is significantly sharper at 24mm f/4. Stopped down, the differences narrow, but the Canon generally produces sharper image quality even at f/8. The Canon has more latCA at the wide and mid portions of the focal length range and also has noticeably more vignetting over that similar focal range at f/4, though the differences are essentially erased by f/8. With a front element that does not extend and retract, the Canon is better weather sealed. The Sigma has a higher MM, (0.20x vs. 0.16x) The Canon's 1mm wider focal length may not sounds like much, but it is a noticeable difference. The Sigma's focus shift attribute is another considerable difference.

The other lens that begs for a comparison is the 12-24mm f/4.5-5.6 DG II HSM Lens, Sigma's previously-released 12-24mm model. Here is a visual comparison of these two lenses:

Although the design of the Art lens is not dramatically different, the f/4 model is considerably larger and heavier. And, the Art's price has grown even more than its weight, making the II appear to be a great bargain.

Is the Art lens's wider aperture useful? For some, the answer is "Yes." For others, not at all. Far more convincing in this decision making process is the image quality comparison. The Art lens handily bests the II in all wide open (matching aperture) comparisons, especially in the corners. The difference remains rather obvious even stopped down to f/8. The Art lens has less considerably less vignetting wide open and still less at f/11. The Art lens has less distortion. Overall, the Art lens is a significant upgrade to the II, but that gain is not without financial cost.

There are many more comparable lenses available, but no options offer a rectilinear focal length wider than 14mm. Use the site's lens comparison tools to make your own comparisons of these lenses.

Summary

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I had the perfect plan to get a great sample photo using the Sigma 12-24mm f/4 DG HSM Art Lens. Photographing the Pennsylvania Capitol building during the blue hour seemed to be a great opportunity for a sure-thing quality sample image from this lens. I picked a clear sky day and was in position well before sunset, with the camera set up and ready to go. The sun set and the ideal moments within the blue hour came and went, but ... the lights on the capitol dome were never turned on. I gave up with about 25 minutes remaining before the capitol visiting hours were over. I ran back around to the front of the building, went the security checkpoint and took a few more interior photos.

After closing time, I checked out some other potential opportunities before picking up the car and driving to nearby City Island to photograph the green and red Christmas-colored lights under a bridge reflecting in the Susquehanna River. As I was photographing these lights, I noticed that the capitol dome lights were now on. Argg.

I decided that I was this close and photographing them would not get much more convenient. But, I didn't want to pay another parking garage fee (I was currently in a 2-hour-free parking spot on the island). So, I lightened my load, taking just the 12-24 Art on an EOS 5Ds R and the tripod in my other hand. I ran/fast walked over a mile back to the capitol, took a set of photos and ran/fast-walked back.

While neither set of exterior capitol dome photos were bad, they were not what I originally envisioned and coming in below expectations is always disappointing. Fortunately, there is digital image compositing. On my second visit that day, I (unintentionally) selected the same focal length (20mm) and nearly identical framing as used in the first visit, resulting in two images that could be overlaid.

I captured some nice interior shots on this day and more importantly, I learned (more like confirmed what I expected) that this is a really fun lens to use. Some product evaluations are more fun to perform than others and this one ranks high up on the list. The Sigma's great overall quality with the extremely wide focal lengths are what drive the fun-ness. This is not a cheap lens, and the focus shift is a notable shortcoming, but it delivered some nice images for me.

A 12-24mm lens is not likely to be the sole lens in a kit, but it will complement nearly all lens kits well. This lens will inspire creativity and provide uniqueness in your imagery.