Sigma 10-20mm f/4-5.6DC EX HSM

About as wide as it gets for DX shooters.


Copyright 2007 Thom Hogan
Sigma 10-20mm mounted on a D300 body. Note the nice balance in size.

Lens Formula
14 elements in 10 groups; 3 aspheric, and 3 SLD elements.
Other Features
Internal focus, 77mm filter size. Comes with hood. Focuses to 9.4" (0.24m).
Size and Weight
About 81mm long, 16.4 ounces (465g).
US$499 (street 12/07)

The Basics

The big sore spot for DX body shooters is really wide angle lens choice. When Nikon first came out with digital cameras using the DX format in 1999 (the D1), there was almost nothing that would get you wider than the 35mm (FX) equivalent of 28mm. About your only choice was the 14mm f/2.8 Nikkor, which, frankly, wasn't up to the job (and still only got you to about 21mm equivalent).

Two Nikkors broke the log jam: the 10.5mm full frame fisheye and the 12-24mm f/4G DX. But both these lenses have things that make them less than perfect: the 10.5mm has a high degree of barrel distortion in it and requires software to correct linear distortion (which means that you can't visualize the actual frame when shooting), and the 12-24mm is a great lens at the top end of its focal range but only a decent one at the wide end.

Since making those two lenses, Nikon has been quiet in the under 28mm equivalent DX range, making only 28-xx equivalents (the recent 14-24mm isn't a DX lens, though a few DX users might end up migrating to it; more on that when I review it). The third parties, however, saw this as an opportunity and produced several alternatives:

  • Sigma 10-20mm f/4-5.6. The subject of this review.
  • Tokina 12-24mm f/4. Very close to the Nikkor in most respects, possibly a bit sharper, but with serious flare issues into the sun and requires much thinner filters.
  • Tamron 11-18mm f/4.5-5.6. Much warmer color rendering than the Nikkor, most consumerish build quality.

With the smaller sensor size of most of the Nikon digital bodies (D2 series, D200/D300, the Fujifilm bodies, etc.), the angle of view for a 12mm focal length is effectively that of a ~18mm lens on a 35mm SLR, so we're talking about lenses that are all under 20mm equivalent here. Since I haven't written about this before, let me give you a feel for what I think about "wide angle":
  FX (35mm) DX
Very wide angle <20mm <13mm
Wide angle 20-28mm 13-18mm
Modestly wide >28mm >18mm

Most newcomers to wide angle lenses think that the primary thing that distinguishes them is their angle of view: a wider lens gives you a wider angle of view on a scene. Yes, you can see more "width" through the viewfinder, but that's actually not the real reason why pros tend to gravitate towards "very wide angle" lenses instead of "modestly wide" ones. The real issue is depth. The wider angle of view allows you to move closer to the nearest subject, which gives you an exaggerated depth in your final image (my workshop students are all chanting: near, middle, far). If you think back to the classic landscape shots, they all tend to have dramatic depth to them, not side-to-side width. Remember, you're going to take a three-dimensional space (reality) and capture it in two dimensions that you're going to print in two dimensions and then display on a two-dimensional surface. Depth is so much more important to a photograph working than angle of view because of that. "Very wide angle" lenses allow you to push depth cues, while "modestly wide" lenses don't.

So what we're looking at here is a lens that allows us to do something that those 18-xxx DX zooms doesn't: move closer into our subjects and add depth to our shots. (A few people will be saying, "but I need more angle of view to take in the entire scene I'm shooting." Yes, that's true. If you were photographing studio apartment interiors in New York City, you probably need as much angle of view as you can get. But I'd still argue that if you don't frame for depth, angle of view alone will give you very uninvolving shots. But that's a subject for another article...)

Compared to the Nikkor, the Sigma is a bit shorter and lighter, though slightly wider in barrel size. The things that make people interested in it are: lower price, wider angle, and lighter weight. Also note that if you shoot with a D40 or D40x, only the Nikkor and Sigma will autofocus on them, so it also is the only alternative for those folk.
Copyright 2007 Thom Hogan The Nikkor 12-24mm on the left, the Sigma 10-20mm on the right. The Sigma is a little shorter in length, but a bit bulkier in width.

The 10-20mm focal range gives you horizontal angle of views from 61 to 99 degrees on a D300 or other similar DX sensor body; that's effectively the same as using an 15-30mm lens on a 35mm film or FX sensor body. Even at the long end of it's focal range the Sigma is still in wide angle territory. Indeed, it goes from "very wide angle" to "wide angle" to "modestly wide," covering pretty much all the wide-ness you might need.

This is a two ring design--the zoom ring is nearer the camera and the focus ring is almost at the front of the lens (i.e. the traditional positions on zoom lenses). The lens extends very little with zooming, and not at all with focusing. The lens has a distance scale, but with no depth of field or infrared markings.

Optically, the Sigma lens is modestly complex, with a 14 element design in 10 groups. It has three aspherical elements and three SD (low dispersion) elements in the design, which is where most of the optical complexity lives (aspherical elements often cause linear distortions that are not, well, linear). One eye-brow raising design choice is the six-blade aperture diaphragm. However, I will say this: unlike many aperture openings I've seen lately, the Sigma keeps its geometric shape perfectly. Moreover, at the wider apertures (f/4-f/8) it either is fully curved or slightly curved in the opening.

The unlabeled hood supplied with the lens is the bayonet type butterfly style. It can be reversed onto the lens for carrying, but it adds significant diameter to lens when you do so (and covers the focus ring, so you won't be tempted to use it this way ;~). It's pretty thin at the side openings, but it does make a difference, so you should always use it, if possible.

You Sigma's wave motor operation with this lens (HSM), which is similar to AF-S, and that focusing will take you down to a little under one foot (.24m, or about 9" for us American blokes). The supplied lens cap is not a pinch-front type, and hard to remove/replace when the hood is on. Do yourself a favor: buy an extra Nikon-style 77mm lens cap and use it on this lens.



I have no real complaints about the build quality of this lens. To be honest, I've absolutely abused it since acquiring it when it first came out. It's been stuffed in backpacks unwrapped, it's been dragged across rock and dirt, it's been exposed to sea spray more times than I can count, and it's got more frequent flyer miles than 99.9% of the folk reading this review. It doesn't exactly look new any more, but it also doesn't show the wear and tear some of my long-use lenses do.

The zoom ring is thin and stiff, though there's no "hitch" in the turn like you feel with some lenses. You can't exactly finger roll the zoom on this lens, but that's not a big drawback, as you rarely do that with really wide lenses.

While there's a small difference in "feel" of the two rings, both rings use a similar stripe pattern. Fortunately, the rings are enough apart that you're not likely to confuse one with the other, as you can on some lenses. Unlike many focus rings, the Sigma's feels quite smooth. From near to far focus is almost a half turn.

Despite what some others have written, I find the Sigma a little more temperamental about filter thickness than my Nikkor 12-24mm. I've moved to thin filters with it, but you should note that the Singh-Ray Vari-ND filter--even the thin version--will vignette at 10mm on this lens. That's a bummer in my book.

The lens balances very nicely on a D200 or D300 (or S5 Pro for you Fujifilm users). Nor does it stick out as much as the Nikkor. Moreover, the lens stays short at its shortest focal, unlike the Nikkor.


Everyone's probably scrolled past all my other comments to get down to this section, so let's cut to the chase: this is a very good lens in almost every respect; but it's not close to perfect. The wide angle DX lens of our dreams still does not exist.

Distortion: Things are a little different for really wide angle lenses. One of the problems that's encountered is unpredictable (or perhaps non-linear is a better word) distortion. At 10mm, this lens has something akin to what's called mustache distortion. At the edges, there's visible barrel distortion while in the center there's almost no visible distortion though there is a small bit of distortion that varies between barrel and pincushion. This is one of the side effects of using quite a few aspherical elements for wide angle lens design. The problem is that such distortions are difficult to remove from the picture. By 14mm, the lens is producing just barely visible pincushion distortion, and at 20mm that has lowered to being essentially invisible. Overall, the distortion handling is much better than you'd expect for such an extreme lens, as at all focal lengths the amount is relatively low. The primary problem is that at 10mm the distortion does become visible at the edges of the frame and is difficult to remove.

Sharpness: Apparently there's some sample variation with the 10-20mm, something I've encountered with a lot of Sigma lenses. Mine tests decently, but I've also encountered one that tests less well.

Center performance is darned good across the board. I really can't complain about it at all. Corner performance leaves something to be desired, at least at the maximum aperture. The best aperture for balancing the center and edge is clearly f/8. Surprisingly, I don't find as much focal length variation as I do on a lot of lenses. Basically the center stays sharp throughout the range, and the maximum aperture is softer in the corners throughout the range. Here's my new short-hand cheat sheet for sharpness:
Sigma Wide Open (f/4-5.6) Optimal Aperture (f/8)

The corner performance does leave something to be desired wide open, and it never reaches any level that matches the excellent center. Still, I find it acceptably sharp for landscape work, where I'm usually at f/11 (note that anything past that will produce clear diffraction issues on the high-end Nikons). Since I'm now using a shorthand table with reviews, I suppose for comparison sake I should include one here for the 12-24mm Nikkor:
Nikkor Wide Open (f/4) Optimal Aperture (f/5.6)
very good
very good
very good
very good
very good

The Nikkor really is let down by its corner performance wide open at the widest focal length. As I've noted before, from 18-24mm it's a very strong performer, one of Nikon's best.

Aberrations: At anything other than the widest focal length, chromatic aberrations are pretty well controlled. When you measure within Imatest you're looking for the average pixel width. For the longer focal lengths, that tends to remain under one pixel for much of the frame, which is what I'd call more than adequate control for a wide angle lens. At 10mm, chromatic aberrations actually increase as you stop down and are worst at the optimal aperture for sharpness (f/8). In the absolute corners I was measuring numbers in the mid-two pixel range at f/8 and 10mm. But I don't know of a lens with this much angle of view that does better. And the problem is more pronounced on high contrast edges (which is what Imatest measures) than it is for the real life objects I tend to shoot. Expect to learn how to use the chromatic aberration controls in your raw conversion software if you use this lens much at 10mm.

By comparison, the Nikkor does less well at 12mm wide open at the shorter focal lengths, but better by f/8 and at the longest focal length.

Light falloff: I'm not overly happy with the vignetting performance. I'd call it mid-pack at best. Wide open you're going to see between a stop and a stop-and-a-third of vignetting, depending upon the focal length (it does better at longer focal lengths, worst at 10mm). Vignetting never becomes a non-issue with this lens, as I always find more than a half-stop of it no matter what focal length and aperture I use (i.e. out to f/11). Still, like chromatic aberration, most recent raw conversion programs allow you to adjust for vignetting, so the higher-than-liked vignetting isn't a fatal flaw.

Again by comparison: the Nikkor 12-24mm is about the same as the Sigma wide open, but is much more usable at smaller apertures. By f/8 there's only about a third-of a stop of vignetting at any focal length.

Focus: It's an HSM lens and focuses just like an AF-S lens for the most part. Not that I use it in autofocus much, but it does snap to focus and doesn't hunt.

Flare: I had no really bad problems with this lens (I should note that I always used the supplied hood). It does as well as you can expect a lens like this to perform, given that huge front element. Essentially, don't shoot into the light source and it is fine. However when you do get visible flare points in the lens they tend to have a large degree of bright green in them, which can be distracting. At the extreme, you often get a narrow rainbow-like flare spot well away from the light source itself, and which has a long, very visible green component. By comparison, the Nikkor produces a larger flare spot much closer to the light source, but somewhat more subdued in color. One other note on shooting into light sources: the six-blade aperture of the Sigma produces a much less interesting diffraction pattern at small apertures when a bright source like the sun is put behind the edge of a near object.

Overall: As many of you have noticed, the 10-20mm Sigma replaced the 12-24mm Nikkor in my bag, and I've been shooting with it for quite some time now (almost two years). You're probably wondering why, as none of the performance points (other than autofocus, which I rarely use) are stellar with this lens. Well, they're not stellar with any other lens that goes that wide, either. Consider that we're at the FX equivalent of 15mm. That means you have to compare this lens at 10mm to a D3 using the 14mm Nikkor or perhaps the 14mm Sigma I've reviewed before. And you know what? When you come at it that way, you discover that the Sigma 10-20mm is about the best of the wide angle bunch for DX-framed cameras, and probably better than the FX frame options to date (I haven't tested the new Nikkor 14-24mm yet). Only the 10.5mm Nikkor fisheye goes wider, and it has more faults. The Nikkor 12-24mm is the clearly better lens at 20mm, but at 12mm I lean slightly towards the Sigma even though the test results would say the slight advantage is still Nikon's (plus, of course, I can go 2mm wider, which is significant for the DX frame). Vignetting and chromatic aberrations are easily dealt with in software these days, so it really boils down to corner sharpness at 10mm for me: is it good enough to be usable? And the answer is, yes, stopped down to f/8 or f/11. The center sharpness of the Sigma 10-20mm at 12mm is slightly better than the Nikkor 12-24mm, so there I have my answer: Sigma by a nose for my work.

But for your work the answer may be the opposite. If you need faster apertures or are shooting at the longer focal lengths much, the Nikkor is clearly a better choice.


  • Corners, corners, corners. Vignetting, softness, and aberrations, oh my.
  • Strange distortions. Not an architectural lens by any stretch of the imagination, despite the low actual distortion percentages.


  • Good enough. I've tested a lot of options in the 10-12mm range, and they all come with liabilities. The Sigma's liabilities are more livable for a landscape shooter than the alternatives.
  • A good value. I've dragged this lens around the world. It holds up to my abuse and gives me that good enough performance I just mentioned. Considering it costs less than the Nikkor, that makes it a decent value, too.
Quick Evaluation

; another modest cost alternative to an expensive Nikkor.


This one was tough. That missing star in performance is all about the corners and into the sun shooting.

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Version of Review:
12/17/07: initial post.
12/19/07: fixed specifications | Nikon | Gadgets | Writing | imho | Travel | Privacy statement | contact Thom at

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