Before I start with this review, I thought it was worth pointing out that Sigma have loaned me this lens in return for images taken with it. I am only doing a review of this lens as it may be useful for other photographers considering purchasing one. I am under no obligation to provide a positively biased report.
I am not going to get nerdy and talk about graphs and technical data. This is a hands-on review about the most important factors when considering a lens.
Sigma’s Art series of lenses are their professional range, made to the highest standards both optically and physically. The 12-24mm f/4 is the latest in the addition to a fast growing family of great optics. I already own the 50mm f/1.4 and the 35mm f/1.4. The former is generally accepted as the best 50mm lens ever made - far out performing the Canon and Nikon equivalents for sharpness, and often being compared to the far more expensive Zeiss lens. Although the 35mm is very sharp, I have always found it to be a bit hit and miss with focusing. I have also tried the 20mm f/1.4 for astro photography and was impressed with the results.
It wasn’t long ago when 24mm was considered “super wide angle” but over recent years there have been a number of great 14mm lenses, and most full-frame wide zooms now start at 16mm, which makes 24mm seem far from super wide. In the past 12 months Canon have released their 11-24mm f/4 L, and now Sigma have come up with their competitor in the super wide zoom market. To give you an idea of how wide this lens is when fitted to a full frame camera, the angle of view at 12mm is a whopping122 degrees.
The first thing you will notice when opening the box of the 12-24mm is that this is a very solidly built lens. Continuing the high production finish of the Art series, the zoom ring is well tensioned and smooth. The focus ring is positioned at the front of the lens which is where it should be. The lens cap is huge, and slips on over the built in hood. There is no clip to hold it place but it fits so well that this doesn’t seem necessary.
Talking of the built-in lens hood, this means attaching filters isn’t as easy and practical as it is for a lens with a front thread. Filter manufacturers such as Lee and Formatt Hitech do make an adaptor but you’ll need super large filters if you want to avoid vignetting at the wider focal lengths. Sigma haven’t included a rear filter holder for the use of neutral density gels, but this is probably due to the way the rear element slightly protrudes from the back of the lens housing at 12mm.
Attaching the lens to the camera makes a satisfying clunk which seems to somehow justify the expense of the lens, in a similar way to the sound a Mercedes car door makes when it closes. Although this is a heavy lens (1.1kg), not being too long makes it feel well balanced in the hand. I had mine attached to a Canon 5Dsr. There is little point in attaching this lens to a cropped sensor body.
There are four things I am most interested in testing with any lens. The first is sharpness across the frame. This is important to me as I sell a lot of large prints, so I’m always looking for tack sharp images right into the corners. Second is contrast. If the shot looks punchy straight out of the camera, it will need less editing, and I try to do as little as possible in this field. Thirdly is flare. Some lenses suffer very badly from scintillation flares, and super wide angle lenses are prone more than any other. Flare can ruin a good image, so a lens which copes well in this area scores major points with me. Lastly is distortion. Out of all these four points however, distortion is the one which can be most easily corrected, so it is of less importance.
As with most lenses, I would expect this one to have a sweet spot around 16mm at f/8 (both middle settings in the lens’s two variable scales). Let’s face it, no one is going to buy this lens to use at 24mm as there are far cheaper 24mm lenses on the market, so I was keen to test this one towards its widest end. This lens does however perform excellently at its longer focal lengths - I'm just not going to post the test shots in this review as I want to concentrate on where its appeal is going to be for most people.
This shot was taken at 14mm at f/11 to try to get sufficient depth of field to hold the lower right corner acceptably sharp. When viewed full screen on my 27” 5k iMac the image looks stunning - bitingly sharp with rich tones.
Zooming into the middle section to 100% shows excellent sharpness. When you consider how smaller part of the image this is, you can appreciate the detail this lens is capable of.
This is the same 100% zoom but this time of the extreme right hand edge. The further away you go from the centre of any lens, sharpness will always drop off. There is a notable reduction in sharpness compared to the centre image, but this would be expected, and in my opinion this is still very acceptable. This is still better than some lenses produce in their centre.
The corners are where any lens will be at its weakest. For this shot I used f/16 to achieve the foreground to be acceptability sharp, so diffraction will be having an impact on the sharpness over the entire frame here. I am also using the lens at its shortest focal length of 12mm, so these two settings are well out of the sweet spot. Even so, the middle of the image is still very good, and the corners are also very acceptable.
Middle section at 100% (above)
Extreme top right corner at 100% (above)
The contrast of this lens is impressive, with rich tones present straight from a RAW file. This is helped by the lens’s ability to cope well with flare. Before using the lens I read the inclosed instructions which warn that “ghosting and flare occur much more easily than on longer focal length lenses". I interpreted this as an admittance by Sigma that this lens may not perform well in this area, but looking at these images here, you will see it actually seems to cope remarkably well. It’s certainly way better than my Canon 14mm f/2.8 L II which is particularly prone to specular flaring, and much better than my old Canon 17-40mm f/4 L.
I was keen to point this lens directly at the Sun to see what happened, and through the viewfinder I couldn’t see any flaring at all. A closer inspection of the image on the computer screen does show minor flare spots (circled in the below image) but these are very subtle and could easily be removed if needed. Of course, the best thing to do is avoid them in the first place by not including a bright Sun in your frame.
Here are a few sample shots of a different scene with lots of fine detail across the frame. As you will see, the centre of the image is sharpest when the lens is wide open at f/4, and the corners are at the best when around f/8. This is no surprise, and goes along with most other lenses, which is why I would look to use this lens around f/5.6 to f/8 where possible to get the best of both worlds. Starting with the original uncropped image, none of these shot have had any editing done. They are flat and unsharpened jpeg conversions from the RAW files.
Vignetting is obvious with this lens when used at f/4 and 12mm, but stopping down to f/5.6 improves things dramatically, and by f/8 it’s really not noticeable. Even at f/4, the vignetting is not a problem as it can be so easily removed if not wanted.
The competition for this lens is the Canon 11-24 f/4 L and the Nikon 14-24mm f/2.8. The focal length at the longest range of all these lenses is identical, but varies at the widest end, which let’s face, is where it matters on a super wide zoom. You may think that 1 or 2mm isn’t going to make much difference, but at these super wide settings it really does. 1mm as a percentage of 12mm is 9%, so the Canon should give a 9% greater angle of view at 11mm than the Sigma at 12mm. When I've used the Canon however, I have noticed it isn't as sharp at 11mm as it is at 12mm, so I find myself using at 12mm anyway.
The price is where the biggest differences can be found between these three lenses, with the Sigma and the Nikon coming in at around £1,650, and the Canon being double this! The advantage of the Nikon is that it is a stop faster, but the only situation where I can see f/2.8 on such a wide angle being of use is for astro and aurora photography.
Using such a wide angle lens requires you to have a large subject and be able to get up close and personal with it. There is no point in standing in a vast open landscape and shooting at 12mm because everything will appear way too small, with any foreground dominating the scene. This lens comes into its own in tight spaces or where you have significant interest and detail within a metre or two of the lens.
Verdict - would I buy his lens? Absolutely I would. The build quality is fantastic, with image quality to match. In fact I would need to look very hard to find anything negative to say about this lens, so it really just comes down to whether you can afford the dent in your wallet and the additional kilogram in your bag.