Sigma is making these two lenses available in either Sony E-mount or Leica L-mount varieties. For this review, I used the Sony E-mount versions on a Sony Alpha 7R III.
Weighing one pound, 6.2 ounces (630 grams) and measuring 4.5 inches long by 3.5 inches in diameter (113.2 by 87.8 millimeters), the 20mm f/1.4 is the bigger brother of these two new wide-angle primes. In comparison, the 24mm f/1.4 weighs one pound, two ounces (510 grams) and measures 3.8 inches long by 3 inches in diameter (97.5 by 75.7 millimeters).
The build quality of both lenses is very similar and, in fact, are designed to be familiar in use with the other currently available f/1.4 DG DN lenses: the 35mm and 85mm. Each is made with Sigma’s tried and true thermo-composite on the exterior, and there’s a mix of matte and semi-gloss finishes. I think having the entire lens in the matte finish would look nicer, but everyone is going to have their own opinions.
The two lenses have matching rings, switches, and buttons. Starting at the lens mount side, there’s first an aperture ring which can either directly control the f-stop, or be set and locked to “A” which will allow the camera to control it. These lenses may also be de-clicked with the on-off switch to the left side. When on, it unmistakably has a loud click to it. When it’s disabled, the ring has good fluid tension to it while not being overly difficult to turn. With one finger trying to move the f-stop up or down a couple of stops, it can’t get much better. The ribbing on this ring is plastic.
Moving up on the lenses there is a focus mode switch, a rubberized focus lock button that’s customizable in the camera’s menu settings, and a manual focus lock switch. The manual focus lock switch is interesting because I don’t remember other lenses I’ve used that have one. What this function will do is allos you to disable the focus-by-wire operation of the large focus ring. It’s not uncommon in astro and landscape photography to switch to manual focus to hold a point of focus for a longer period of time, and this takes it to the next step where the ring cannot be accidentally nudged by a couple of degrees either once it’s set. I love seeing features like this that clearly have come straight from real photographers’ requests on what would help them do their work.
Speaking more about the focus ring, it does have rubberized ribbing, unlike the aperture ring. It’s a great feeling ring with no play or crunchiness in the rotation. It glides smoothly once it gets in motion, but it is a bit on the stiff side.
The front of the 20mm lens has 82mm filter threads and the 24mm has 72mm filter threads. However, these lenses also have a rear gel filter holder. I haven’t picked up on the appeal of lenses that have rear filter holders for gels since it’s still totally confusing on which gels are pure enough for optics and which are for lighting equipment and I can’t be the only one. I wish lens manufacturers that offered this would either include a variety of gels themselves if they’re supposedly so cheap or give specific product recommendations on what to put back there.
The Sigma 20mm f/1.4 DG DN Art uses 17 elements in 15 groups, including two SLD and three aspherical elements. The Sigma 24mm f/1.4 DG DN Art uses 17 elements in 14 groups, including two FLD, one SLD, and four aspherical elements. They both have Super Multi-Layer Coating like all current Sigma lenses and both also use Nano Porous Coating. Both of these coatings are to suppress flare and ghosting issues.
The image quality looks outstanding for both lenses when at their best, and still perfectly fine when some effects like lens flares crop up. The flaring becomes more noticeable the more the lenses are stopped down and, for the most part, it is tasteful and not too heavy. As far as color fringing — otherwise known as chromatic aberration — this, too, is well controlled for both, and I didn’t notice anything pop out at me when shooting with corrections turned on in the camera.
One thing that will be hard to miss is the vignetting when the lenses are shot wide open. It cleans up quickly as the lens is stopped down, but you will need to make some corrections needed in post if this is not the desired effect. Sigma shared a pre-launch profile correction with me and for both lenses, it wiped away the vignetting without further effort on my part. Once the lens begins shipping to customers, these automatic corrections should be made available in popular photo editing software.
Taking a closer look at image sharpness, I saw that for the 20mm lens, it held together really well throughout the aperture range. At the center of the image, f/8 was perhaps the best, but it was hard to tell when everything looked good. There was a slight dip at f/16, the lens’ maximum aperture. At the corners, f/5.6 through f/8 looked sharpest.
Sharpness for the 24mm was a similar story, with f/8 looking overall the best at the center and f/8 being the best at the corners.
These lenses both feature an 11-bladed rounded aperture and the quality of bokeh they produce is wonderful. With such a wide-angle field of view and shallow depth of field, having these pleasing out-of-focus elements in the image really adds dimension to the scene.
After spending some time with both optics, I am finding that I am a fan of both of these new lenses. With that, it makes which one to truly recommend a little more difficult. Having both of them in my camera backpack at the same time, I had no strong feeling of going with one over the other in any situation: they come away with comparable results in every way. I just came to think of them as the big one and the small one.
If it really does boil down to that for you, I think I’d have to recommend going with the small one — the 24mm — unless you are quite certain that you need the slightly wider angle of view.
Are There Alternatives?
While the Sigma 20mm f/1.4 DG DN is the only 20mm f/1.4 lens available other than the Sigma DSLR 20mm lens it is replacing, I still think it has some tough competition with the Sony 20mm f/1.8 G. With the Sony, we obviously lose two-thirds of a stop of light however, the benefits to going with the Sony for the same $900 price show themselves in weight and size: the Sony 20mm is only 13.2 ounces in weight and is 3.3 inches long and three inches in diameter.
The Sigma 24mm f/1.4 is probably the best you can do at this price, but Sony does offer its highly-popular 24mm f/1.4 G Master lens for $1,300. This is many hundreds of dollars more expensive than Sigma, but it’s actually harder to tell the clear and obvious benefits in this case. Perhaps side-by-side testing would prove one over the other, but I would go with the Sigma for the lower price and comparable specs.
Should You Buy Them?
In both cases, yes. Sigma has proven with the f/1.4 DG DN Art series that it is not trying to make lesser versions of Sony’s best lenses to fill in some niche, but instead are downright in direct competition against them — and successful in this endeavor, I might add.