Introduction: The bad attitude
In the past, when I was working in a photo store, the aversion towards other than original lenses (especially Sigma) was really overwhelming. A common malady of these lenses was that the same lens types differed from piece to piece and sometimes fell apart after half year of usage. An internal joke was that every Sigma lens purchase should include some free instant glue.
These lenses also had issues with back-focus. Not to mention the fact that older Sigma lenses had to be re-chipped to work with newer digital SLRs. I have seen a lot of frustrated customers so you can imagine my attitude towards this specific brand. This was ten years ago.
In this article I am reviewing the Sigma 18-35mm f/1.8 DC HSM and I am also comparing it with the Nikkor 35mm f/1.8 and Nikkor 17-55mm f/2.8.
When Sigma released information about its new lens concept in September 2012 I was skeptical at first. They announced plans to divide and reorganize their interchangeable lens business into three product lines – Contemporary, Art and Sports; each line for specific photography needs. After the announcement of new lenses like 35mm F1.4 DG HSM, 50mm F1.4 DG HSM, and 18-35mm F1.8 DC HSM, I began to rethink my mostly negative, opinion. Then some superb reviews from credible authors and well-known websites were published and my attitude changed slightly. I wanted desperately to test some of the lenses. Are they really that good? Do they deliver a crisp image? Are they well-made and is the handling smooth?
Hands on preview
The Sigma 18-35mm F1.8 DC HSM lens (from herein referred to as Sigma 18-35mm) has attracted my attention because it’s the first lens in the world that has a constant 1.8 aperture within the whole zoom range. It is a DC lens, which means it is specifically made for small sensor cameras. You can mount it to a full frame camera but the result will be a tunnel view or heavy vignetting. In Nikon cameras it covers the range 27 - 52.5mm when calculated for the full frame. It is not a big zoom lens, but actually it covers the range from a medium wide to normal focal distance, which can make it a practical companion. A regular street price for the lens is about $800 USD (700€).
The lens itself comes shipped with a lens hood and a lens bag. This leaves a good initial impression on our first meeting. The lens bag is a solid padded case with inner foaming, no cheap textile bag whose only purpose is collecting dust in a shelf. The lens case fitted perfectly in my Lowepro rucksack and was instantly “ready to go”.
I have to admit, the lens is a little bit long as I have expected. It is longer than my AF-S DX Zoom-Nikkor 17-55mm f/2.8G IF-ED I usually use. It reminds me more of a tele-lens than a wide-angle lens. Reviews on the Internet say that the Sigma 18-35mm is heavy with its 28.2 oz. (800 g), but it felt pretty well and confident in the hand. The 17 glass elements inside the lens and the internal focusing mechanism call for its price. The Sigma 18-35mm is therefore a little bit heavier and longer (4.76”, 12.1cm). A surprise is the internal zooming, that means the lens stays the same size all the time. That is impressive! The lens stays the same on 18mm and 35mm and the front lens doesn’t rotate, kudos Sigma!
A good way to hold the camera while walking is to grab the camera at the mount where the lens is attached to the body instead of holding the camera body itself. The center of mass lies somewhere at the camera mount (because of the lens’ weight) and it is convenient to hold it in this way, especially when you take pictures for a longer time period and you want to have the camera ready. When taking pictures it won't take long for you to find the proper support stance when you hold the lens from the bottom. Sigma 18-35mm is not stabilized therefore it needs a good grip when shooting at lower speeds.
To my big surprise it has a lower filter diameter (72mm). I would expect a 77mm or 82mm filter thread on this fast wide-angle zoom lens. The body itself is made from a thermal stable composite, metal (the mount is made from plated brass as well) and the zoom and focus rings are made from rubber. The rubber rings feels very pleasing in the hand. You can find a switch for manual and automatic focusing on the left side and a distance scale on the upper side.
A comparative test
I wanted to test the limits of the lens like lens flare, backlight, distortion, vignetting, purple fringing and chromatic aberration. For this test I also brought the AF-S DX Zoom-Nikkor 17-55mm f/2.8G IF-ED and AF-S DX Nikkor 35mm f/1.8G (from herein Nikkor 17-55mm and Nikkor 35mm) in order to compare the results to each other.
I chose these two lenses because the Nikkor 17-55mm is similar with its focal range to the Sigma 18-35mm lens and the 35mm fixed focus competes with the fast aperture. Nikkor 17-55mm is an older lens, it was designed 10 years ago in 2004, it is still produced by Nikon and can be bought for around $1300 USD (1200€). The Nikkor 35mm was firstly produced in 2009 and it became a popular prime lens for Nikon DX cameras, also because of its price close to $200 USD (150€).
For this test I shot the same location with all three lenses with different aperture settings. The lenses are all set to 35mm. With the Sigma 18-35mm and Nikkor 35mm on the short end with apertures 1.8, 2.8, 4, 5.6, 8 and 16 and with Nikkor 17-55mm starting with aperture 2.8. The shots are made from hand therefore they don’t match exactly, but I try to stay with the focus at the same point. The pictures are taken in NEF format for to preserve the uncompressed richness of the detail.
I placed the camera in front of the arbor not only to capture the details of the ornamentation, but also to see the sharpness of the tree branches in the corners and the purple fringing at the edge of the bright and dark parts. The white balance on Nikon D3200 is set to a fix value, the sensitivity on ISO 100 and the metering is center-weighted.
I have to admit I am impressed. The overall sharpness of the Sigma 18-35mm is very good. It shows very small and decent purple lines, all the details are visible and nothing looks wishy-washy. There is some slight vignetting in the corners and it appears to be not as sharp as the Nikkor 35mm, but it can be the branches were moved by the wind. I have to take another test with an object standing still. The colors are just right, the autofocus works very well, but I will test the AF later on moving subjects. The Nikkor 35mm looks a little bit sharper as the Sigma 18-35mm, but the purple fringing is awkward, I haven’t expected to see that much of it.
Now all three lenses together: focal point 35mm, the same distance, the same object, the same wide 2.8 aperture and the same light and location. It’s hard to tell the winner, the Nikkor 35mm shows more details as the Sigma 18-35mm, but it still shows this purple fringing. Personally I like the image from the first two lenses, the image from the Nikkor 17-55mm is somewhat dull, like through a smoke veil.
The Sigma 18-55mm is a clear winner with f/4. Stepped down to aperture f/4 it is unstoppable in terms of quality: no visible vignetting, no unpleasant purple lines but a crisp and vigorous image from the center to the corners. It beats the fixed focus Nikkor 35mm and the Nikkor 17-55mm. The Nikkor 35mm seems to be less sharp at f/4, which is not something I expected. I also assumed that the Nikkor 17-55mm will hold up at this aperture, but apparently it has to be stopped down more.
At aperture f/1.8 the Sigma 18-35mm and Nikkor 35mm are at the same quality level with the Nikkor a little bit sharper. The Nikkor 17-55mm simply can't hold the quality level and I am disappointed of this fact: it still shows some purple fringe and has this smoky look with lower detail. I think the Sigma 18-35mm is sharpest at aperture f/4, but the corners of the lens looks best at f/8. Unfortunately, I can’t continue at aperture f/16 with this test, because I am apparently the owner of two shaky hands. So let’s do another lens-to-lens comparison with a tripod.
A comparative test number two
An old brick wall is a good challenge to test the lens’ performance. Usually a wall is a good way not only to text the lens resolution, but also to show the barrel distortion and vignetting when shot from the front.
In the second test you can observe how the quality of the image changes with a different aperture. The image shows cropped images with aperture f/1.8 to f/22 with missing space for f/1.8 by Nikkor 17-55mm and f/22 by Sigma 18-35mm. The Sigma 18-35mm maintains its quality through the whole aperture range with a slight decrease in corner sharpness at aperture f/1.8 and an overall blurred image at f/16 – its lowest aperture setting. Compared to the Nikkor 17-55mm it is a very good result. The Nikkor 17-55mm shows some chromatic aberration in the corners at f/22.
I haven’t noticed any visible vignetting or barrel distortion at 35mm.
Now it’s getting interesting. The Nikkor 17-55mm show the least blur in the corners, but it is also the lens with the lowest overall sharpness at 35mm focal distance. The Nikkor 35mm shows a sharpness peak at aperture f/5.6 – f/8, but otherwise is its image blurry, not to mention the purple fringing. The Sigma 18-55mm is visibly sharp already at f/1.8 with its peak at f/4 and then abruptly decreasing at f/16. Attention, a razor-sharp lens.
The board game test
To test the vignetting and barrel distortion of Sigma 18-35mm thoroughly I need some geometrical patterns. A board game will serve this purpose very well; it has a solid color background to test the vignetting and some straight lines to test the distortion. The camera is placed on a tripod and it points right to the center. The images from the park showed very good results in terms of vignetting and distortion, but I want to be 100% sure.
As you can see on picture above, the vignetting is really low. This is an astonishing result for a fast aperture at f/1.8 and a wide zoom lens. Such slightly dark corners can be easily corrected in post-process using appropriate software without losing any image quality.
The vignetting is still present and I think it got bigger at the 35mm as it was at 18mm. Nevertheless, it is really subtle and can be easily corrected as well. The vignetting is barely noticeable in real life photographs, it appears only at aperture f/1.8 to f/2, but from f/2.8 it’s practically invisible.
Wide lenses tend to show serious barrel distortion especially at the short end. The Sigma 18-35mm has some as well, but it’s well suppressed and controlled, also because of the fact that its focal range is not very long. I have placed a pattern of lines onto the original picture to make the distortion more visible to the viewer’s eye. Also the cropped section of the image helps to demonstrate it. Tests from other users on photo-websites say there is also a pincushion distortion at 35mm, but actually I couldn’t observe this phenomenon. Both barrel and pincushion distortion can be well managed by a computer software, e.g. Adobe Lightroom.
DOF and blur
Even if the 18-35mm range is not really made for separation of an object from the background, it shows some very pleasant bokeh and background blur. On the image below you can see that even with a wide lens the girl stands out from the image and the objects and people in the background are gently blurred.
One has to be careful with the autofocus: the aperture f/1.8 shows a similar depth of field on a crop sensor like the f/2.8 on a full frame. This means the autofocus has to be precisely set; otherwise there is a great chance to find out later (as one usually does at home on their computer monitor) that the desired object is not exactly focused, which is always frustrating. More advanced Nikon cameras with a fast and precise autofocus have an advantage over lower models here. Even if I couldn’t compare the lens on two bodies, there is statistically a lower chance of misfocusing with a 51- (Nikon D7100) or 39-point (Nikon D5300) autofocus than with an 11-point (Nikon D3300).
The Sigma lens has 9 rounded diaphragm blades, which produce delightful and attractive looking out-of-focus points of light – the bokeh. It is particularly visible at the long end of the lens at a 35mm focal length. The bokeh is not swirly in the edges of the image (as it tends to be on the Nikkor 35mm when compared); it is uniformly shaped and bright across the entire width of the image. The Sigma bokeh was the best of the three tested lenses.
The Sigma 18-35mm is not a macro lens, but it has a maximum magnification ratio of 1:4.3 and it lets you get near to an object. You can get as close as 28cm/0.92ft, which is a highly useable distance. I was excited when I made the images of the small plastic figures how close the camera can be moved to the subject while the figure stays sharp. This is great for everyday use, for holidays, creative images, documentation etc., although I have encountered difficulties with a correct focus because of the shallow depth of field. Tethered shooting with a tablet was a good solution; I could focus precisely to the desired point. Otherwise it is quite an obstacle to get the desired place into focus, nearly impossible through a viewfinder, less painful with the zoom function on the LCD. The picture quality is good as I expected, there is some chromatic aberration visible on close subjects (as you can see on picture number 22), but becomes less visible when the lens is stopped down to f/4.
Outside in the city park
Sunday’s weather lured young and old to enjoy the sparkly sunlight and fresh spring air. I wanted to test the lens in real life conditions. I saw a group of youngsters and obtained permission to shoot test images. Some of them jump on a rope and some of them stand on their head while juggling. The Sigma 18-35mm has a fast autofocus. It is nearly silent (only very little noise). The autofocus can be adjusted during the AF mode (full time manual focus), which is very convenient. One does not have to switch to MF to adjust the focus distance. The f/1.8 aperture is supercool. I get so much light, even in darker spaces, that I can freeze the pose of a guy on a rope without a motion blur – with ISO 100 (picture 23). Also here again one has to be careful with the autofocus. It has to be precisely set; otherwise there is a great chance to find out later (as one usually does at home in post-process) that the desired object is not exactly in focus. Images shot with wide aperture and with other then the center autofocus point tend to be not exactly focused, but this depends on many circumstances: the light intensity, contrast of the object, moving of the object, etc.
Sigma’s autofocus is really fast. I hadn’t any problems to re-focus on fast scenes, the autofocus it is silent, smooth and accurate. The sound of the autofocus is noticeable in a video only in a silent space, it wasn’t noticeable in an open space full of louder noises. Sigma 18-35mm uses a HSM (Hyper-Sonic Motor), it is similar to Nikon’s SWM. In terms of noise the Nikkor 17-55mm is less noticeable then the Sigma 18-35mm, but both are very quiet. A loud autofocus motor can be disturbing not only during videos, but also when taking photos of animals in the wild or during a wedding.
The next “problem zone” I wanted to see is the lens flare. Today’s lenses are multicoated with special layers to prevent the light from bouncing back and forth within the lens’ intestines. Sigma has shown very little of the flare. Of course it can be seen some time and at specific angles, but it is very well reflected, as you can see in the picture above, where the sun shines directly to the lens.
What shall I say... I am speechless. This lens turned me upside down, from a (nearly) Sigma hater to a Sigma lover. This lens is an ideal companion for everyone who can appreciate a shallow depth of field, a fast aperture and a wide focal length. With its image quality it can even replace a fixed focal lens, so instead of buying two or three prime lenses, you can carry around only one. The sharpness from corner to corner can only be praised even with aperture wide open, an ideal lens for action, wedding and indoor photography. It is not an extremely wide lens, for architecture or landscape photography there are other alternatives.
The Sigma 18-35mm F1.8 DC HSM is made for a demanding photographer that can appreciate a fast lens, looks for high quality and can handle a shallow depth of field, but doesn’t want to spend too much money on prime lenses with similar quality. The Sigma 18-š5mm is made for DX only; on a Nikon D610 or D800 you will experience a “tunnel view”. It would be probably too heavy, too big and too expensive if made for full-frame cameras. Sigma lacks an image stabilizer, so it’s not the right lens for the video makers unless with a steadycam to reduce vibrations.
The Sigma Corporation set a new trend in lens making, a relatively cheap, fast and optically crisp lens.
And a 3-year extended warranty. And the possibility to change the lens mount, if you choose another brand (Canon, Sony, Sigma, Pentax) in the future. And the optional USB-dock to customize the lens settings and adjust the focusing. Sigma clearly threw down the gauntlet. I can’t to wait see the answer from Nikon.
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