L-Mount Alliance 5 The Sigma lens is still fairly big despite those design upgrades because it covers a full-frame sensor, opens to F1.4, and is razor-sharp all the way around. For all of that, the barrel must contain some large, weighty glass. Although Sigma is made of lightweight materials like polycarbonate and aluminum, you cannot defy the laws of physics. At this angle of view, we don’t anticipate that the majority of photographers actually require an F1.4 lens. However, this is a great alternative if you enjoy searching for beauty in the shadowiest areas, creating photographs of the night sky, or pursuing soft, blurred backgrounds.
0 (Credit: Jim Fisher) Similar to its full-frame weather-protected camera bodies, Sony’s rival FE 20mm F1.8 G lens has weather sealing as well. As it only has sealing at the lens mount, the Sigma 20mm F2 DG DN Contemporary isn’t designed for cloudy or wet days. Since neither Leica nor Panasonic now offer a 20mm or 21mm L-Mount prime, the 20mm F1.4’s weather resistance is a defining feature for users of L-Mount systems.
DIRECTION AND CONTROLS
1 (Credit: Jim Fisher) We enjoy the 20mm F1.4 Art’s many on-barrel controls. The manual focus ring, which surrounds the lens body and has customary rubberized ridges to aid with grip, is the most noticeable.
I used an
L-Mount Alliance 6 and the Sony E version of the lens to test it. Manual focus is nonlinear when those factors are combined. Therefore, turning the ring quickly results in more aggressive focus shifts, while turning it slowly results in more thoughtful, accurate adjustments.
2 (Credit: Jim Fisher) Although nonlinear focus is more popular among photographers because to its adaptability, videographers may find it difficult as they cannot set focus markings for repeated focus racks. Owners of L-mount systems are in a different situation since those cameras let you choose between a linear and a nonlinear focus response in the menu. We like the Sony FE 20mm F1.8 G for video because of its linear focus response and reduced weight, which makes it a better alternative for drones like the
L-Mount Alliance 7 and L-Mount Alliance 8.
Image 13: Sony a7R IV, 1/2,000-second shutter speed, ISO 100 (Photo by Jim Fisher) Another issue for videographers is the focus breathing effect, which is extremely noticeable. When you focus closely, the lens displays a wider angle of vision because the angle of view changes in tandem with focus. The lens is safe to use for the majority of video types, but rack focus shots that switch between subjects are not recommended.
Driven by an STM stepping motor, autofocus. Focus is quick enough and silent, which is good for video. On the a7R IV, the lens moves from its closest focus distance to infinity in 0.3 seconds during testing. The lens generally stays up, but you could notice a lag if you’re way out of focus when you start. It takes roughly 0.15 seconds to expose an image and sharpen a slightly out-of-focus shot. On-barrel AF/MF toggles allow you to quickly switch between focus settings.
2 (Photo by Jim Fisher) The lens also has an aperture ring for adjusting the f-stop in addition to the focus ring. It can be adjusted in third-stop steps from f/1.4 to f/16, and a toggle lever lets you switch on silent, click-free operation. You can choose the A position or lock the aperture controls to the lens using a second toggle. The f-stop must be set using the camera body controls once the toggle is in the A position.
Sigma has an on-barrel function button that by default controls the AF-ON setting. However, you can alter the button’s functionality on the majority of cameras. A Lock toggle simultaneously disables the manual focus ring and turns off that button. When you want to lock focus and maintain it on the stars during nighttime sky work, it comes in helpful.
4 f/16, 100 ISO, 1 second, Sony a7R IV (Photo by Jim Fisher) This 20mm lens is not a macro lens, but it does focus quite closely (about 9.1 inches from the sensor or just a few inches from the front element). It can produce very spectacular photographs with expansive backdrops and yields respectable 1:6.1 life-size results. Remember the extremely affordable
L-Mount Alliance 9 if you like the concept of using a wide prime for macro photography; it is incredibly sharp and affordable, however it takes a while to focus. Do not forget that the Sony FE 20mm F1.8 G also achieves 1:4.5 magnification.
5 f/2.8, 1/400 sec., ISO 100, Sony a7R IV (Photo by Jim Fisher) ART 20MM F1.4 DG: I used the 20mm F1.4 DG DN Art and the 60MP Sony a7R IV together to test the resolution of the camera in a lab setting and at night. Our SFRplus test chart is evaluated by
Sony E-Mount 0 software, which reveals that the lens performs almost flawlessly. Even at the f/1.4 aperture, we saw results that are very close to the 5,000-line threshold that we deem exceptional for the a7R IV’s sensor.
Image 16: Sony a7R IV, ISO 100, 1/125 sec., f/11 (Photo by Jim Fisher) Wide open, the 20mm F1.4 exhibits 4,900 lines throughout the majority of the frame, with corners that continue to exhibit excellent contrast (4,200 lines). For photographers capturing photographs of the night sky, this makes a significant difference because they may get crisp results without shutting down the lens. Edge-to-edge results at the largest aperture are desired in astrophotography for practical reasons.
I’m not much of an astrophotographer, and the light pollution near my house in the Philadelphia suburbs prevents me from taking vibrant Milky Way pictures. My photographs of the night sky, which depict pinpoints, still support Sigma’s claim that its optical formula will reduce
Sony E-Mount 1. Other astro-specific features include an on-barrel Lock that maintains focus even if the focus ring is bumped and a flared barrel design that keeps lens Sony E-Mount 2 (a substance used by astronomers to reduce condensation and fogging) out of the frame.
7 f/1.4, 8 seconds, ISO 400, Sony a7R IV (Photo by Jim Fisher) Technically, I was pleased with my astrophotography, but if you’re a serious astrophotographer, I suggest reading evaluations from experts to make sure the 20mm F1.4 meets your requirements. The 24mm F1.4 DG DN Art, which is also promoted for astro work but didn’t perform as well in our tests at suppressing sagittal coma, is another Sigma astro lens if you prefer a somewhat narrower angle. Additionally, Sony offers the
Sony E-Mount 3, which has an even wider field of vision and effectively prevents coma but is much more expensive ($1,599).
7 f/1.4, 2 seconds, ISO 100, Sony a7R IV (Photo by Jim Fisher) The edges will blur in more typical f/1.4 use circumstances. For example, landscape photographers frequently use tighter apertures, and from f/5.6 through f/8, the effects are excellent from the center out. Diffraction reduces detail with the high-pixel a7R IV at f/11 through f/16, but you might still wish to use those settings to get the sunstar effect. The 22-point starbursts produced by an 11-blade aperture are an unusual appearance. We recommend the Sony FE 20mm F1.8 G’s sunstars for landscape photographers who seek the effect, even though the sunstars I obtained from the lens have a few fuzzy lines.
Although wide lenses don’t normally have good bokeh, it’s not too difficult to get the blurred background effect with this lens as long as the subject and background are separated by a sufficient distance. We’re pleased with the way the blur has turned out as well; the out-of-focus highlights are rounded, have soft edges, and don’t appear cluttered.
8 f/16, 1/400 of a second, ISO 100, Sony a7R IV (Photo by Jim Fisher) Some optical compromises, most notably some discernible barrel distortion, are made up for by in-camera adjustments. You won’t have to worry about this problem if you use your camera in JPG mode, but we anticipate that many users of this lens—especially astrophotographers—will wind up using a Raw processing program. Sigma gave us a Raw correction profile to use with the lens in
Sony E-Mount 4; it successfully reduces vignetting and effectively corrects distortion at f/1.4.
Chromatic aberrations are not a major issue in this case. In test images, I couldn’t see any lateral CA. When present in a photograph, this effect appears as purple fringing around dark objects against bright skies and is simple to identify near telephone wires and tree branches.
9 Sony a7R IV at f/1.4, 1/1,000 of a second, and ISO 100 (Photo by Jim Fisher) In the somewhat blurred focus transition areas, longitudinal chromatic aberration (LoCa), a distinct phenomenon, frequently manifests as misleading purple and green colors. This effect is effectively muted by the 20mm F1.4, however it is not entirely gone. When examining photographs, I had to zoom in to a 200% magnification to see the effect, which is seen in the detail of the Master Lock emblem on the padlock in the image above. In the majority of real-world settings, it is unlikely to be a significant issue.
A STANDOUT FOR SPECIALISTS IN WIDE-ANGLE
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