Sigma 15mm F1.4 DG DN Diagonal Fisheye Art

The Sigma 15mm F1.4 DG DN Diagonal Fisheye Art ($1,999) is the first autofocusing fisheye lens for mirrorless systems we've tested. Available for full-frame E-mount and L-mount cameras, it matches an incredibly wide angle of view (180 degrees diagonally) with a class-leading f/1.4 aperture that's ideal for night sky imaging. And its creative possibilities don't stop there—the lens is quite useful for ultra-wide angle interiors, landscapes, and cinema. But you have to make peace with tendency to show false color in the bokeh and soft wide-open rendering at close distances, not to mention its premium price. Overall, the Sigma 20mm F1.4 DG DN Art earns our Editors' Choice award for astrophotography because it costs just $899, has an equally bright maximum aperture, and suits more subject matters. But don't count out the 15mm Fisheye if it meets your needs.

A Stout, Dense Full-Frame Lens

The 15mm F1.4 Fisheye is a heavyweight as far as prime lenses go. It tips the scale at 3.0 pounds and measures 6.3 by 4.1 inches (HD). The size isn't out of the ordinary, however, once you consider its light-gathering capabilities and 180-degree diagonal angle of view. It compares favorably with the similarly minded Sigma 14mm F1.4 DG DN Art (5.9 by 4.0 inches, 2.6 pounds), another lens designed for night sky imaging. The 14mm F1.4 has a shorter focal length but its angle of view is narrower. Whereas its optics properly draw straight lines as straight lines in images, the 15mm F1.4 Fisheye draws them as curves that reveal heavy barrel distortion. The effect gives the fisheye category its name—the extreme angle is similar to what fish see. The Sigma 20mm F1.4 Art (4.5 by 3.5 inches, 1.4 pounds) is fairly large as primes go but not as much to carry as the 14mm or 15mm options.

(Credit: Joseph Maldonado)

The construction quality is phenomenal just like other Sigma Art entries. A matte black barrel that mixes polycarbonate and magnesium materials houses the optics. The plastic components are of high quality—Sigma refers to the material as Thermally Stable Composite (TSC) and I've no reason to doubt the company's claims that TSC is as strong and durable as aluminum. Internal seals reduce the chance of dust and water ingress, while the bulbous front element has an anti-smudge fluorine coating. You can wipe fingerprints away with a microfiber cloth in most instances without leaving any smudges.

(Credit: Joseph Maldonado)

You'll likely use this lens with a tripod since it's necessary for astrophotography. A tripod also makes it much easier to set a lens plum and center it on other wide-angle subjects. But you shouldn't use your camera's tripod socket in this case, since the lens would make your system too front-heavy. The good news is that Sigma includes a rotating tripod collar and foot mid-barrel. The collar rotates a full 360 degrees but doesn't include detent stops. As such, you need to visually match up a pair of painted white lines to set it level or use your camera's digital level. If you're using the lens for technical imaging and architectural interiors, make sure to add a bubble level to your hot shoe if your tripod doesn't already have one. The collar is easily removable—it slides right off the back without any tools and uses a knurled thumbscrew for setting its tension. Meanwhile, the magnesium foot includes dovetail cuts so it can go directly into an Arca-Swiss tripod without an additional quick-release plate.

(Credit: Joseph Maldonado)

The big front element precludes the use of threaded filters, though a rear filter holder supports gel inserts if you want to add a neutral density (ND) filter to limit incoming light for long exposures and video. A built-in lens hood provides some protection against damage. The hood includes a ridge that makes it easier to mount a lens heater, a type of accessory that helps prevent condensation and fogging during chilly nighttime photo sessions.

(Credit: Joseph Maldonado)

Sigma sells the 15mm F1.4 in two mounts. I reviewed the E-mount version for Sony cameras, but you can also get it for L-mount, which Leica, Panasonic, Sigma, and other brands support. In either case, the lens works with both full-frame and APS-C sensors, though its angle of view is tighter on the latter (22.5 degrees in full-frame terms).

Few Fisheye Competitors

There's no true competitor for this prime. I've never tested a lens with such a wide angle and aperture before. The combination is ideal for night sky images, so it's not surprising that Sigma markets this lens strongly toward astrophotographers who wish to capture scenes with the aurora borealis. A fisheye is useful for other types of scenes, too. For instance, you can capture an entire view of a tight interior space or convey a feeling of disorientation in cinema projects. Given its distorted perspective, the lens is more suitable for crafting special effects shots than capturing reality. If you want an astrophotography lens without such an extreme perspective, the aforementioned Sigma 14mm, 20mm F1.4, and 24mm F1.4 DG DN Art all qualify.

(Credit: Jim Fisher)

There are a few manual focus fisheye lenses with more pedestrian f-stops on the market worth a mention. I reviewed the Samyang 12mm F2.8 (originally made for SLRs) years ago and the same lens now sells for mirrorless mounts under the Rokinon brand name. I haven't tested more recent budget-line entries like the 7artisans 10mm F2.8 ($256), AstrHori 12mm F2.8 ($256), or TTArtisan 11mm F2.8 ($215), however. All three are quite affordable, available for E- and L-mount cameras, and manual focus only.

(Credit: Jim Fisher)

As for autofocus options, the Canon EF 8-15mm F4L is usable on mirrorless cameras via adapters, the Sigma MC-11 for E mount and MC-21 for L mount. Although its narrower aperture makes it less desirable for astrophotography (it gathers just one-eighth the amount of light as the Sigma), the Canon is a bit more versatile in terms of focal coverage. It can create fully circular fisheye photos at 8mm and frame-filling diagonal shots when you zoom in.

Handling, Controls, and Focus

The 15mm Fisheye's stout barrel has plenty of room for on-lens controls, and Sigma uses it well. The lens includes discrete rings to set the aperture and adjust manual focus, a customizable function button, and switches to swap the focus mode (AF/MF), lock manual focus, change the aperture ring response, and lock the aperture control.

(Credit: Joseph Maldonado)

The aperture control scheme is standard for Sigma Art lenses. In the A position, you must set the f-stop via the camera body. With the ring set in its numerical range, you can directly control the aperture from the lens. It supports an f/1.4-16 range with clicks at third-stop increments or smooth, continuous movement. Again, it just takes a flick of the switch to change between the two options.

(Credit: Joseph Maldonado)

The manual focus lock is a more curious addition. It's standard on Sigma's line of astro-tuned lenses, including the 14mm F1.4, 20mm F1.4, and 24mm F1.4 DG DN Art. It comes in handy since camera autofocus systems simply aren't good enough to lock focus on stars at night. If you're making these types of photos, you need to do so carefully and take advantage of your electronic viewfinder's (EVF) magnification to punch in on your subject. It takes some time and practice to set focus on stars, and the lock simply eliminates the possibility of accidentally nudging the ring and throwing your scene out of focus.

(Credit: Jim Fisher)

It's not hard to set focus exactly with this lens since the control ring is properly dampened and has a long, 180-degree throw to move between close-up (15.2 inches) and infinity. I noticed a small amount of focus breathing in testing. The lens shows just a little bit more of the world around the edges at close focus distances compared with distant ones, but this isn't a concern in most scenarios. If you're using the lens for self-recorded vlogs, the changes in distance between camera and subject aren't significant enough to show the effect. And if you have a scene that calls for a rack from a near to far subject, background blur will hide any breathing. There's no reason to rack focus at narrow apertures since the depth of field puts everything in focus already.

(Credit: Jim Fisher)

Creators looking at the lens for landscapes, architecture, and other terrestrial subjects can use autofocus instead. The lens uses Sigma's High-response Linear Actuator (HLA), which proves both speedy and accurate. When I tested the lens with a Sony a7R IV, the focus locked on nearly instantly and silently. That's good news for video use too, as focus changes won't introduce any noise to a soundtrack.

(Credit: Jim Fisher)

The 15mm Fisheye focuses at just 15.2 inches from the sensor, which works out to around 8 inches from the front element for a 1:16 reproduction ratio. As such, you can get close-up shots of small subjects with dramatically broad backgrounds. The only drawback to using the lens for these types of images is a soft detail rendering at f/1.4. Close-up image quality vastly improves by f/2.8, however, at which you still get ample background blur in the near macro range. Sigma's other F1.4 astro lenses don't show soft results at similarly close distances. For example, the 20mm F1.4 focuses to 9.1 inches for 1:6.1 reproduction.

15mm Diagonal Fisheye: Image Quality Analysis

I typically use Imatest to evaluate lens resolution but don't have a test chart suitable for testing fisheye lenses. Without hard data, a qualitative analysis will suffice. When I tried photographing distant subjects, anything more than a couple of feet away from the lens, the results were sharp and detailed even at the maximum f/1.4 aperture. But, as mentioned, results look soft to my eye at close focus distances and the wide-open setting.

(Credit: Jim Fisher)

The aperture supports a minimum f/16 setting, but using it yields softer results than in the f/5.6-11 range. Optical diffraction (light particles scatter as they pass through a very small diaphragm) is responsible for the drop in clarity and the detail loss is noticeable upon close examination. There's still reason to stop down to f/16, however, if you want to see the sunstar effect around bright points of light. The 22-point starbursts from the lens look a bit soft but can still add impact to a landscape scene. I noticed some rainbow false color when I incorporated the sun into photos at f/16 (a result of light bouncing around inside the lens) but it's not a serious problem.

(Credit: Jim Fisher)

On the plus side, the 15mm F1.4 Art handles the sun and other bright light sources quite well at wider apertures. It controls flare competently and does a good job of avoiding false color from internal reflections from f/1.4-11. This is good news since a lens this wide is likely to capture the sun or another backlight in the frame during the daytime. The image below of a large fern shows the type of flare you can expect at wide apertures with the sun just outside of the lens' view.

(Credit: Jim Fisher)

Fisheye lenses are not ideal for scenes with defocused background bokeh, but you can still achieve the look. You just need to focus on a subject that's pretty close to the lens and put some distance between it and the backdrop. In these situations, the lens draws soft, defocused backdrops even once you stop down to f/2.8 for maximum sharpness. The blur falls shy of being buttery smooth, however, as some objects in the background remain discernible. I also spotted quite a bit of false color from longitudinal chromatic aberration (LoCA). On a more positive note, the circular defocused highlights show soft edges and avoid any ugly false texture.

(Credit: Jim Fisher)

The 15mm Art is a good fit for astrophotography, as mentioned. Its wide view can capture large swaths of the night sky while still incorporating landscape features. True to Sigma's marketing, the 180-degree angle is ideal for photos of the northern lights. And Sigma tunes the optics to get good detail of faraway subjects at the maximum aperture. Furthermore, the bright aperture makes it easier to manually focus on a dark sky and allows for shorter shutter durations that sidestep motion blur that the Earth's rotation causes. I recommend stopping down to the f/2.8-8 range for daytime landscape scenes, but you should still use use the lens wide-open to reduce the exposure time and keep the camera ISO low for night sky pictures.

(Credit: Jim Fisher)

I'm by no means an expert astrophotographer and deal with too much light pollution in my neighborhood to get good pictures of constellations or the Milky Way galaxy, so I handed the lens off to the astronomy expert on PCMag's staff, Tony Hoffman, to give it a try. His results show crisp stars with little evidence of sagittal coma, even for those at the edge of the frame. Sagittal coma is a distracting effect that draws stars with protruding spines and false color halos. While Sigma's other astro lenses—the 14mm, 20mm, and 24mm F1.4—all capture narrower angles of the night sky, their star detail and coma control are just as good.

(Credit: Tony Hoffman)

On the downside, it's pretty easy to spot a vignette at the corners in the f/1.4-2 range. Make sure to apply some vignette corrections in post to brighten the corners for astro pictures. Stars also appear quite sharp; the Fisheye is clearly tuned to get its best wide-open pictures for distant subjects, so there's no need to stop down as is the case when focusing close.

Distortion is a feature of this lens, but you could always straighten its lines in Photoshop or Lightroom if you snap a picture and want to avoid the fisheye look. That somewhat defeats the purpose of the lens, as distortion correction narrows its angle of view.

(Credit: Jim Fisher)

Verdict: A Premium Fisheye for Astro Specialists

The Sigma 15mm F1.4 DG DN Diagonal Fisheye Art is foremost an astro lens, but any photographer who wants to capture an extremely wide view is sure to enjoy its ability to craft special effect shots. Its optics and controls are both optimized for use after the sun sets, while a sturdy construction means it can survive harsh weather in remote locations away from light pollution—albeit for a premium price. Another Sigma lens, the 20mm F1.4 DG DN Art, remains our Editors' Choice winner for night sky photography thanks to its lower price and more practical rectilinear wide-angle optics that support a broader range of use cases. To put it plainly, the 15mm F1.4 Fisheye is a specialty lens, while the 20mm F1.4 Art has appeal for both astrophotography and other, more general disciplines.