The Sigma 20mm F1.4 DG HSM ART – The Fastest, Widest Angle Lens in the World Tested

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Not Your Father’s Sigma

When Sigma announced its first “Art” series lens a couple of years ago, many scoffed at the notion that Sigma, long a 2nd-tier lens manufacturer, could compete with the big boys at Canon and Nikon, let alone lens makers like Zeiss. Well, a lot can change in a couple of years, and no one’s scoffing anymore.

With 11 lenses now in the Art Series (8 for SLRs, 3 for mirrorless), Sigma has produced a solid range of top-quality lenses for the professional and prosumer market, covering the range of 20mm – 105mm (FF), in both fast primes and zooms. When I heard that Sigma had upped-the-ante again with their just-released 20mm F1.4 DG HSM A, the fastest, widest lens on the market, at a very impressive $899 price point, I had to take a look.

Sigma has long produced a 20mm f1.8 lens, a fast, but middling-quality lens for the low-light shooting crowd. The 20 1.8 sells for about $450 used, and I decided to compare the two and see if the new 1.4 was worth twice the cost.

The Sigma 20mm F1.4 DG HSM A vs Sigma 20mm F1.8 DG – Physical Impressions

The first thing you notice comparing the two lenses is the build quality. The 1.4 feels better than a Canon L or Nikon pro lens; in fact, if you removed the branding you might think it’s a Zeiss. Because of this and the fast f-stop, it’s a very heavy lens, at 950g (2.1lbs), and a little over twice the weight of the 20mm f1.8. It’s a sleek, polished beauty of a lens with a nice focus ring, though it must be said, not quite as nice as a great manual lens for focus feel, though this is to be expected of an AF lens. It looks and feels more than commensurate with its price. The 1.8, on the other hand, is very run-of-the mill, perhaps a small step up from a 18-55mm kit lens in feel, but not much of a step.

The 1.4 has a semi-spherical front element and a permanently attached hood, and uses an unusual end cap which fits over the entire end of the lens, as pictured. Unlike many of the ultra-wide end caps of this sort (for instance, as found on the Tokina AT-X 16-28mm f/2.8 Pro, it is tight-fitting and good at keeping out dust. The downside is that it is simply a friction-fit; there is no spring-loaded catch to keep the hood in place. I was initially concerned about this arrangement, but after scrabbling over rocks in the desert for a few hours with this lens on a sling with no lens-cap issues, it seems to be a workable arrangement. The 1.8 has a flat front element, and uses the usual spring-loaded cap and reversible hood, which is included with the lens.

The Sigma 20mm F1.4 DG HSM A vs Sigma 20mm F1.8 DG – Shooting Impressions

The first thing you notice about the 1.4 is the autofocus is fast and almost perfectly silent; a marked contrast to the very noisy and slower AF on the 1.8. This is, without question, a fully modern AF system on par with Nikon and Canon’s latest efforts.

I shot the two lenses on a Nikon D800 under varying conditions, swapping lenses between shots to keep conditions as consistent as possible, given I was shooting outdoors for many shots. It’s worth noting that before beginning this comparison, I tuned each lens for my particular D800 body using the body’s micro-focus adjustment. This is an option available to those of us using pro or prosumer bodies, but for those with bodies which don’t feature micro-focus adjustments, it should be noted that Sigma has release a USB dock for the A series lenses which allows for micro-focus adjustment via Mac or Windows computers, using a Sigma-supplied software. Interestingly, the Sigma software allows you to adjust not only the focus distance (to correct front or back focusing), but allows you to choose your preferred level of focus speed vs focus accuracy, tailoring your lens for studio vs action sports use, for instance. This unique USB dock runs $59, and is compatible with all A series lenses. It also allows firmware updates to be uploaded to the lens, which is definitely a boon for 3rd party lenses, in particular.

First up we have following “Italian Futurist” shot, for lack of a better term, taken at f1.8 for both lenses:

Click on the photo, then use your left/right arrows to switch between them – the lens in use appears below the photo. Hit ESC to back out.

First of all, you’ll notice the POV is slightly different in these shots, which is because the lenses are different physical lengths, though the tripod was not moved between shots. From this very first shot we see the wide disparity in quality between the two lenses. Note the 1.4 is brighter overall, much more consistent across the frame, brighter in the corners (vignetting), and sharper in all areas, with better contrast as well. The 1.8 tends to get pretty “muddy” in the corners, which I found to be an issue under all conditions. The 1.8 shows mediocre rectilinearity (lack of barrel distortion or pincushioning) across the frame, with the 1.4 is much less distorted – this is most visible in the post at the right edge of the photo. Also of note is the detail in the LEDs inside the glass bowl – the focus point for this photo was a certain point on the wire, and the bulbs in the 1.4 shot are significantly less diffuse than the 1.8 shot. The one criteria the 1.8 wins in is comma – the 1.4 displays much more comma than the 1.8, as you’ll notice in the reflections of the lights – they are round in the 1.8, whereas they are vertically stretched, and in some cases repeated, in the 1.4 shot – that is comma.

The next shot is the engraved frame of an old Austrian piano, which I mention because it drives me crazy when photos leave me to wonder what I’m looking at.

The first two shots are full width, and the following two square shots are crops, showing detail. Again, we see the 1.8 is softer than the 1.4, with less contrast and detail.

Next, we have a sunset shot taken at f1.8:

Here, we see a sharpness and brightness advantage across the board for the 1.4, though it’s most noticeable in the corners of the frame, as illustrated by the corps of the trees on the blue background in pictures 5 and 6.

Palms at night:

Aside from the lack of detail we see in the 1.8 shot, note the crop showing the extensive fringing visible in the harshly lit trunk of the tree, which is far better controlled in the 1.4 photo. Note that this I shot wide open for both lenses; the 1.8 shot was taken at f1.8, and the 1.4 shot at f1.4. This serves to show how much sharper the 1.4 is, even wide open.

Lastly, a shot of rocks in the desert, taken at f2 on both lenses:

Here, again, we see better sharpness, and less vignetting from the 1.4, as well as greater contrast. Notice also the extreme difference in sharpness at the bottom center of each photo.


I believe the photos show the Sigma 20mm F1.4 DG HSM A is a far superior lens to the Sigma 20mm F1.8 DG, but it is also twice the price, if you buy the 1.8 used – keeping in mind the 1.4 is not available used at this time. Whether it is worth the increased cost depends upon your budget and your intended use. If you shoot primarily for web use, the difference between the two is minimized, and perhaps the 1.8 is the better value. If you’re on a tight budget, the 1.4 can probably wait, at least until it’s available used at a discount. If you are looking for quality, however, the 1.4 outperforms the 1.8 in every category other than price and comma, which is something typically of concern only to astrophotographers. I can also say that before switching to Nikon, I had the Canon 24L f1.4, which, along with the 135L, were my favorite lenses, and this Sigma 1.4 is an intrinsically better lens (and far cheaper than the 24L). I was really hoping the comparison would be closer, because I’m always looking for a good deal on a good used lens, but after spending a week with each of them, I’m afraid I have to bite the bullet and keep the 1.4. Sigma has simply made such an exceptional lens, at a relatively affordable price, that I just can’t give it up.

2 Responses

  1. Matthew
    | Reply

    Thank you! I was looking for this exact comparison and you delivered and its even greatly written with attention to detail 🙂 I guess ill spare for the 1.4 then and enjoy the better image quality.

    • John
      | Reply

      Very happy that you found it useful. The price difference is substantial, but the quality is there, no doubt.

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