Excellent lens - sharp and WIIIIDE!

Introduction

Ever since purchasing the Nikon D70 I have been longing for that lovely wide angle I used to have with my old EOS-100.

You see, it is not easy to achieve true wide angle coverage with a half-frame digital SLR: due to the crop factor of the D70, an ultrawide 20mm prime is suddenly turned into a, well, kind of mediocre 30mm lens. To be able to get the equivalent of a 18mm ultrawide, you need to purchase a 12mm lens. That's wide. And certainly not cheap.

Of course, with such extreme wide-angle rectiliear lenses, you will always need to know what to expect - objects around the edges of the frame will look "drawn out" and "squashed". If you tilt the lens upward, objects will start to lean in towards the middle of the frame and if you have faces outside the center of the frame, they will look hideously distorted. Just remember, this is not a malfunction, but the normal perspective distortion that comes with the territory.

(With digital image editing software, you can easily turn the rectilinear images into fake fisheye images using the "spherize" tool, where the squashing effect will be minimized to the expense of straight lines now being rendered as curves.)

The competition

So, what's out there in this range? There are as far as I know only two lenses that would fit the bill: the Sigma 12-24 EX, and the Nikon 12-24 DX. (Tokina has just released their version of this zoom, but that wasn't available at the time I wrote this review). Both the Nikon and the Sigma are zoom lenses aimed towards the semi-pro / pro segment. Hence, none of these lenses are cheap, especially the Nikon, costing about 50% more than the Sigma, so it certainly has a heavy impact on the budget of an amateur photographer.

Before actually committing myself to the Nikon 12-24 DX, I had the opportunity to test both the Sigma and the Nikon for a few days. I didn't bother trying to perform any kind of structured scientific comparison between the two, I just kept shooting with both lenses to see which one of them would suit my needs the better. After these days, I feel quite confident to say that both lenses are excellent in one way or another. So let's see what I found!

The comparison

The Sigma is a full-frame lens, meaning that on a full-frame camera, it will give an amazingly wide image. The Nikon on the other hand is a DX lens, which basically means that it will only work on the D-series digital D-SLR's, such as the D70 or the D100. If you attach the lens to a full-frame Nikon body, you will have to zoom in considerably (to around 16 mm) for the heavy vignetting to disappear.

The Sigma is much heavier and bulkier, while the Nikon looks almost just like a normal everyday medium zoom lens if you don't look too close. The Sigma will immediately draw attention to itself because of its staring huge front lens, while you can much more easily get away without too much attention in a crowd with the Nikon.

The Sigma looks a bit unpolished and I found the zoom ring a bit too stiff for comfort - although that would probably loosen up with time. The Nikon on the other hand is smooth and surprisingly lightweight, its physical size belieing the awesome imaging power hidden inside its shell. For shorter excursions, biking or trekking, I would probably find that the Sigma would stay home a lot more often than the Nikon.

My test sample of the Sigma also appeared to be somehow flawed with the focus plane wandering between consecutive shots and a rather strange focusing noise, something that I found a bit worrying. The Nikon is equipped with the AF-S system featuring Nikon's Silent Wave Motor and focuses silently, exactly and swiftly.

The Nikon takes standard 77 mm threaded filters at the front while the Sigma can only be used with awkward gel filters at the back, or alternatively huge 85 mm filters threaded at the front in the lens cap holder ring, which in turn will introduce some pretty nasty vignetting at 12 mm. The usage of various gradient filters are quite common with landscape photography, and the ability to use standard 77 mm filters could easily be a decisive factor for serious landscape shooters. I always have a Hoya multicoated UV-filter attached to all my lenses to protect the front glass from scratches, water spray, dust and smudges and the Sigma wouldn't let me do even that.

The Sigma is a significantly slower lens than the Nikon, and it requires plenty of light for most hand-held shooting. For best image sharpness, you should stop down both lenses a great deal, which in most cases will bring the shutter speed to around 1/20 sec or slower with the Sigma. For landscapes, where you can use long shutter speeds and a tripod, this really doesn't matter, but the Nikon is definitely brighter and is hence more suitable for everyday casual shooting.

When looking at the results, it becomes very clear that the Nikon is exceptionally sharp throughout the entire zoom range. Around the 24 mm end it actually homes in on prime lenses, but even at the 12 mm end it is one of the most beautifully rendering wide angle zoom lenses I've ever had the pleasure to work with as long as you keep the aperture down to around f/8.

Upon scrutinizing the images, it is evident that the best image quality is found near the middle of the frame, and from there on, sharpness successfully drops towards the edges, where also some color fringing starts to appear - nothing alarming and nothing that won't clean up gracefully with Nikon Capture as long as you shoot RAW - but still there.

The Sigma is softer overall, but this lens on the other hand maintains the same consequent image quality throughout the entire frame. I found the image rendering a bit "muddy" compared with the Nikon, but near the edges of the frame, the Sigma wins hands down. The Sigma also appears to have almost no chromatic aberrations whatsoever and is surprisingly free of distortion. Straight lines are rendered completely straight, while the Nikon displays a slight barrel distortion near the 12 mm end, something to remember if architectural photography is your main goal. Personally I won't lose any sleep over this.

Flare seems a bit more prominent with the Sigma, but it is a very graceful flare that never really looks disturbing - I almost kind of liked the effect. You will be forced hard to come up with bad flaring with the Nikon, as long as you keep the front lens clean. Of course, framing the sun in your images is bound to cause some weird artefacts, especially with the D70, where you will often find absurd blooming effects around the sun - but that of course has nothing to do with the lens, but with the camera.

Finally, as I pointed out earlier, the Sigma is a full-frame 12-24 lens - as far as I know it is unique in that respect. The Nikon is intended to be used with half-frame sensor cameras such as the D70 and will lose some of its width when used with full-frame sensor cameras.

Conclusion

After having tested both these lenses for a few days, I finally decided to go for the Nikon. Although a lot more expensive, it appeared to be more well-built, a lot slicker and easier to carry around, something that is absolutely vital for my shooting style. It is faster and produces a generally sharper image than the Sigma. Around the far end of the range (20 - 24 mm), the sharpness is impeccable at f/8 and smaller - nearly as sharp as the 18-70 DX kit lens.

I still need to point out that the Sigma is a brilliant lens, more than adequate for serious semi-pro or pro photography. It has a consequent edge-to-edge image quality, absolutely no distortion and virtually no chromatic abberrations. I know several pro photographers swearing by the Sigma, but for me and my shooting style, the difference in image and build quality and physical size was more than worth the difference in price between the two.

Today, the Nikon 12-24 DX is definitely one of my favorite lenses and for me it is definitely worth its fairly high price. Whenever I leave home with my D70, the Nikon 12-24 DX is never far behind!