Sigma 20mm F2 DG DN Contemporary Lens Review

The Sigma 20mm F2 DG DN Contemporary Lens is a member of the Sigma "I series", "Premium Compact Primes" for mirrorless cameras. These lenses are designed for "photographers who value the experience of taking a picture just as much as the quality of the results." [Sigma]

The Characteristics of lenses in this series include small size, light weight, and affordable price. Also consistent with lenses in this series are precision metal build quality and excellent image quality, with a useful focal length completing the attractive Sigma 20mm F2 DG DN Contemporary Lens package.

The I series lens reviews will reflect the similarities of the lenses in this series.

Focal Length

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Make focal length selection a priority when choosing a lens because focal length matters. While focal length determines the working distance and, therefore, perspective, wide-angle focal lengths are a lot about making foreground subjects large in relation to the background subjects and about including a lot of background in the frame. This angle of view is notably able to give the viewer a sense of the presence in the images captured by it.

The 20mm angle of view makes it a great "scapes" focal length. This angle of view is useful for photographing most scenes that "scapes" can be naturally appended to, including landscapes, nightscapes, cityscapes, buildingscapes, roomscapes, etc.

Include peoplescapes in that list, with environmental photos of individuals and groups captured at a wide range of locations from scenic landscapes to birthday parties in small rooms being a 20mm capability. Note that if multiple people are in the 20mm frame, their distance from the camera should not vary by a significant amount. Otherwise, those in the front will appear larger than those in the back. Avoid getting too close to people for additional perspective issues.

Weddings are a great use for this lens. Think of a bride getting ready with her attendants surrounding her. Think of the first dance at the wedding reception, with this lens capturing the bride and groom large in the frame with the guests encircling them in the background.

Are you photographing architecture? This lens is a great choice for that pursuit.

While the 20mm angle of view is rather wide for use as a general-purpose lens, there are general-purpose uses for 20mm. For example, I've used a 20mm lens to capture an entire day of family holiday festivities. This lens is fun to carry around with a creative purpose in mind.

Videographers will find a host of uses for 20mm.

I like to view focal lengths in comparison format, and since this lens has only one focal length, I'll borrow a few comparisons from zoom lens reviews.

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On an ASP-C/1.5x sensor format body, the 20mm focal length provides an angle of view similar to a 30mm lens on a full-frame sensor format body with an angle of view just slightly narrower than the 28mm example shared above. The 30mm angle of view is only moderately wide and only modestly wider than the ultra-popular and useful 35mm focal length. While there is some overlap in usage between the 20mm and 30mm focal lengths, they are rather different, with 30mm having more general-purpose appeal and uses that better align with the 35mm focal length.

The angle of view provided by the 30mm focal length is a great choice for capturing a natural perspective. It is wide enough to capture the big scene but not so wide that people and other subjects are readily distorted by the close perspective invited by ultra-wide angles.

The 30mm angle of view is a great choice for photojournalistic uses. Wedding and portrait photographers like 30mm, especially for mid to full-body portraits and for group portraits. Landscape photographers have plenty of use for the 30mm angle of view.

30mm is also popular with videographers, especially for creating documentaries. Many medium and large products can be captured at the 30mm angle of view. I'm always happy when a lens with the same or similar angle of view (or a zoom covering this angle of view) comes across my desk because I know that I can assign it around-the-house use.

The complete list of 30mm angle of view uses is long, and I've only scratched the surface here.

Following is a small set of results captured while walking around for a couple of hours with only 20mm available (most examples are from different lenses).

No, post-processing was not used to create that perfectly-placed shadow. Showing up at the right place at the right time meant that a field house shaded all but the first lane on this university track. Also aiding in emphasizing the "1" was the perspective. With the 20mm lens positioned closer to the "1" than the other numbers, the "1" becomes the largest in the frame and, therefore, the most prominent. Everyone loves the number "1", and there are far more uses for an emphasized "1" than any other number.

Once the shadow crept over the "1", I found the scene less interesting and moved on.

On the football field inside the track, the "20" yard line number seemed appropriate to photograph at this focal length though finding a good camera position proved challenging. Shooting straight on the number was not creating an especially interesting composition, but at an angle seemed to work better. The arrow beside the 20 did not fit well into the frame and in the end, I opted to include part of it with the other visible numbers fully contained. The sun was low and bright, making a shadow selfie a requirement from this position.

Moving to a position farther down the track made another shadow selfie as easy as "1 2 3".

An administration building had caught my eye, and photographing it was part of this evening's to-do list. The blue hour is a great time to photograph architecture, and starting with a shooting direction away from the sunset provides the earliest brightness balance between the building lights and the sky.

This camera position required an upward angle to fit the building in the 20mm angle of view, and the leaning walls reveal this.

As the sky darkened, the light balance on the other side of the building, looking toward the sunset (brighter sky), improved.

It was winter, and there was little flora to work with, but the leading lines of a curving sidewalk help draw a viewer's eye into the frame.

The camera direction for the last image of the evening was also toward the now fully set sun with a darker sky included in the frame.

To get a level camera for this perspective required fully extending the Really Right Stuff TVC-24L Mk2 Carbon Fiber Tripod legs and positioning the feet as close together as possible without risking stability.

Proved on this evening was something I already knew — it is fun to walk around with the 20mm focal length in hand.

Max Aperture

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For a 20mm prime lens, f/2 is a relatively wide aperture. No full-frame zoom lenses covering 20mm open wider, and few 20mm prime lenses open wider (though Sigma offers an f/1.4 option).

A wide aperture, allowing significant amounts of light to reach the imaging sensor, provides tremendous benefits. Use that light to enable action (subject and camera) stopping shutter speeds in low light levels, along with low ISO settings for reduced noise. A 20mm f/2 lens can be handheld indoors under average ambient light without image stabilization or ultra-high ISO settings.

Another advantage of a wide aperture lens is the background blur it can create. F/2 with a close subject creates a shallow DOF that draws the viewer's eye to the in-focus subject. It is hard to blur the background diffusely with a wide-angle lens, but the relatively wide f/2 aperture aids greatly in that regard.

Here is a look at the widest apertures this lens avails.

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The f/2 example above illustrates the maximum blur this lens can create. Compare the aperture of your fastest 20mm lens with the f/2 result to see the benefit that f/2 would bring to your kit.

At a reasonably close working distance, the background objects remain recognizable at f/2. Still, they are blurred strongly enough to show separation from the subject.

At longer distances, especially in reduced size images, the f/2 background blur is subtle. Here is another look at the maximum blur this lens can create:

The advantages of a lens with a narrow max aperture are the smaller size, lighter weight, and lower cost associated with smaller lens elements. Despite the wide f/2 aperture, this lens retains those advantages.

This lens features a gear-like, 1/3-stop clicked aperture ring that enables a manually-selected aperture. The camera controls the aperture setting when the ring is in the A (Auto) position. All other settings electronically force the aperture to the chosen opening.

Aside from a slightly more complicated design, I find inadvertent aperture changes the primary disadvantage of an aperture ring. Incorporating a lock for this ring would eliminate that issue, and learning not to grasp the aperture ring when mounting the camera reduces the problem.

Image Stabilization

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The Sigma 20mm F2 DG DN Contemporary Lens is not optically stabilized. Fortunately, Sony takes care of that omission with Steady Shot or IBIS (In-Body Image Stabilization) in their mirrorless cameras. In addition to reducing camera shake, the stabilized imaging sensor provides a still viewfinder image, enabling careful composition. Sensor-based AF takes advantage of the stabilized view for improved accuracy.

With no IS switch on the lens, the camera menu must be accessed to enable or disable IBIS, a slight impediment to working quickly, such as going from tripod to handholding.

Image Quality

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Stellar image quality is what we have come to expect from the Sigma I series lenses, and the Sigma 24mm F2 DG DN Contemporary Lens delivers on this expectation.

This lens produces extremely sharp center of the frame results wide-open at f/2, with only a slight improvement seen at f/2.8.

Often, subjects are placed mid-frame in a composition. Moving farther out on the image circle, where light rays are refracted to a stronger angle than in the center, lenses typically show decreased sharpness.

Fortunately, this one shows only a modest, gradual decline in peripheral sharpness at f/2, and it is primarily caused by decreased contrast due to peripheral shading. Still, this corner performance is remarkable for a 20mm lens. With the shading clearing substantially at f/2.8, extreme full-frame corners are sharp, and by f/4 and f/5.6, the extreme corner performance is outstanding.

The resolution chart is merciless on image quality, so let's take the testing outdoors. Next up are a series of center-of-the-frame 100% resolution crop examples. These images were captured in RAW format using a Sony Alpha 1 and processed in Capture One using the Natural Clarity method. The sharpening amount was set to only "30" on a 0-1000 scale. Note that images from most cameras require some level of sharpening, but a too-high sharpness setting (usually the camera's default) is destructive to image details and hides the deficiencies of a lens.

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These results look great.

Next, we'll look at a comparison showing 100% resolution extreme corner crops captured and processed identically to the above center-of-the-frame images. The first result set is from the bottom left, and the others are from the top left. The lens was manually focused in the corner of the frame to capture these images.

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Samples taken from the outer extreme of the image circle, full-frame corners, can be counted on to show a lens's weakest performance. As mentioned, peripheral shading is impacting the corner contrast at f/2, but the resolution remains quite good. The corners improve rapidly as the aperture is narrowed from wide-open, and stopped down, this lens delivers impressive corner performance.

This performance makes the Sigma 20mm F2 DG DN Contemporary Lens a strong candidate for uses that require sharp corners, including landscape and architecture photography.

This lens does not exhibit focus shift, the plane of sharp focus moving forward or backward as the aperture is narrowed (residual spherical aberration or RSA). Many modern lenses automatically correct for focus shift, though focus breathing (more later) can create slight angle of view changes.

When used on a camera that utilizes a lens's entire image circle, a lens can be expected to create peripheral shading at the widest aperture settings. Wide-angle, ultra-wide aperture lenses tend to show strong peripheral shading wide open, and as mentioned, the over-3.5-stops of shading in the f/2 corners are noticeable. By f/4, the corner shading decreases to approximately 3-stops, and about 2-stops remain in the f/4 corners. Beyond f/4, little additional peripheral shading clears, with a noticeable about 2-stops of shading still darkening the f/16 corners.

APS-C format cameras using lenses projecting a full-frame-sized image circle avoid most vignetting problems. In this case, the just over one-stop of corner shading showing at f/2 may be visible in select images, primarily those with a solid color (such as a blue sky) in the corners.

One-stop of shading is often used as the visibility number, though subject details provide a widely varying amount of vignetting discernibility. Vignetting is correctable during post-processing with increased noise in the brightened areas being the penalty, or it can be embraced, using the effect to draw the viewer's eye to the center of the frame. Study the pattern shown in our vignetting test tool to determine how your images will be affected.

Lateral (or transverse) CA (Chromatic Aberration) refers to the unequal magnification of all colors in the spectrum. Lateral CA shows as color fringing along lines of strong contrast running tangential (meridional, right angles to radii) with the mid and especially the periphery of the image circle showing the most significant amount as this is where the most significant difference in the magnification of wavelengths typically exists.

With the right lens profile and software, lateral CA is often easily correctable (often in the camera) by radially shifting the colors to coincide. However, it is always better to avoid this aberration in the first place.

Color misalignment can be seen in the site's image quality tool, but let's also look at a worst-case example. The image below is a 100% crop from the extreme top left corner of an Alpha 1 frame showing diagonal black and white lines.

Only black and white colors should appear in these images, with the additional colors indicating a modest presence of lateral CA.

A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light. More simply, different colors of light are focused to different depths. Spherical aberration along with spherochromatism, or a change in the amount of spherical aberration with respect to color (looks quite similar to axial chromatic aberration but is hazier) are other common lens aberrations to observe. Axial CA remains somewhat persistent when stopping down, with the color misalignment effect increasing with defocusing. The spherical aberration color halo shows little size change as the lens is defocused, and stopping down one to two stops generally removes this aberration.

In the real world, lens defects do not exist in isolation, with spherical aberration and spherochromatism generally found, at least to some degree, along with axial CA. These combine to create a less sharp, hazy-appearing image quality at the widest apertures.

The examples below look at the defocused specular highlights' fringing colors in the foreground vs. the background. The lens has introduced any fringing color differences from the neutrally-colored subjects.

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The color separation showing at f/2 is relatively strong, but the results improve rapidly as the aperture opening is reduced.

Bright light reflecting off lens elements' surfaces may cause flare and ghosting, resulting in reduced contrast and sometimes interesting, usually destructive visual artifacts. The shape, intensity, and position of the flare in an image are variable, dependant on the position and nature of the light source (or sources), selected aperture, shape of the aperture blades, and quantity and quality of the lens elements and their coatings.

Sigma's Super Multi-Layer Coating and Nano Porous Coating (NPC) are applied to this lens's elements. Apparently, those coats in conjunction with the lens design are effective as practically no flare effects show in our standard sun in the corner of the frame flare test, even at narrow apertures.

Flare effects can be embraced or avoided, or removal can be attempted. Removal is sometimes challenging. Thus, high flare resistance is a welcomed trait of this lens.

Two lens aberrations are particularly evident in images of stars, mainly because bright points of light against a dark background make them easier to see. Coma occurs when light rays from a point of light spread out from that point instead of being refocused as a point on the sensor. Coma is absent in the center of the frame, gets worse toward the edges/corners, and generally appears as a comet-like or triangular tail of light which can be oriented either away from the center of the frame (external coma) or toward the center of the frame (internal coma). Coma clears as the aperture is narrowed. Astigmatism is seen as points of light spreading into a line, either sagittal (radiating from the center of the image) or meridional (tangential, perpendicular to sagittal). This aberration can produce stars appearing to have wings. Remember that Lateral CA is another aberration apparent in the corners.

The image below is a 100% crop taken from near the top-right corner of an a1 image captured at f/2.

These average brightness stars appear to be having little explosions, but from a relative perspective, they look quite good.

A weakness of this lens is the geometric distortion it creates. Expect this lens's strong barrel distortion to make curves out of straight lines in the periphery of the frame.

With increasing frequency, manufacturers are relying on software over physical lens design to handle geometric distortion. Most modern lenses have correction profiles available (including in-camera), and distortion can easily be removed using these. Still, geometric distortion correction requires stretching which is detrimental to image quality.

As seen earlier in the review, it is easy to illustrate the strongest blur a lens can create, and wide-angle lenses are inherently disadvantaged in this regard. Due to the infinite number of variables present among all available scenes, assessing the bokeh quality is considerably more challenging. Here are some f/8 (for diaphragm blade interaction) examples.

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The first example shows defocused highlights being slightly mottled in their fill, but the 9 rounded aperture blades keep the circles relatively round. The other examples are 100% crops that look normal and nice.

Except for a small number of specialty lenses, the wide aperture bokeh in the frame's corner does not produce round defocused highlights, with these effects taking on a cat's eye shape due to a form of mechanical vignetting. If you look through a tube at an angle, similar to the light reaching the frame's corner, the shape is not round, and that is the shape we're looking at here. Below are upper left quadrant crops captured at the specified aperture.

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The cat's eye truncation is not strong at f/2. As the aperture narrows, the entrance pupil size is reduced, and the mechanical vignetting absolves, with the shapes becoming nearly circular at f/4.

A 9-blade count diaphragm will create 18 point sunstars from point light sources captured with a narrow aperture. In general, the more a lens diaphragm is stopped down, the larger and better-shaped the sunstars tend to be. Wide aperture lenses tend to have an advantage in this regard, and this lens is capable of producing nice stars, as illustrated in the f/16 below.

The rays forming the star points would likely fully close and align at f/22, though I am rarely willing to accept the diffraction-caused softness of f/22 images.

The design of this lens is illustrated above. "Construction includes three high-precision glass-molded aspherical lens elements, one SLD element, and one FLD element to suppress a range of optical aberrations." [Sigma]

Overall, the Sigma 20mm F2 DG DN Contemporary Lens turns in excellent image quality. Strong barrel distortion and vignetting, along with some color separation, are this lenses weaknesses, but sharp detail rendition, including at f/2, will overcome those factors for many.

Focusing

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Driven by a stepping motor, the Sigma 20mm F2 DG DN Contemporary Lens's AF system performs with good speed. The focusing is internal and quiet, with only a slight buzz heard during AF.

With adequate contrast on the subject, this lens focuses in extremely dark environments. As usual, the focusing speed is significantly slower in low light.

In AF-S and AF-C modes, the Sony a1 refocuses for every shutter release press, including when the subject is already in focus. This practice leads to increased focus lock times.

Unless one is primarily using manual focus, a lens's autofocus accuracy is important for realizing the ultimate image quality capability of a lens, and this lens has performed well in this regard.

FTM (Full Time Manual) focusing is supported in Sony's DMF (Direct Manual Focus) mode with the shutter release half-pressed or the AF-ON button pressed.

Normal is for the scene to change size in the frame (sometimes significantly) as the focus is pulled from one extent to the other, referred to as focus breathing, a change in focal length resulting from a change in focus distance. Focus breathing negatively impacts photographers intending to use focus stacking techniques, videographers pulling focus, and anyone critically framing while adjusting focus. This lens produces a big change in subject size through a full extent focus distance adjustment.

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The Sigma 20mm F2 DG DN Contemporary Lens features a gear-like metal ribbed focus ring. Located immediately behind the lens hood, the focus ring is easy to find, and though not huge, it has sufficient size.

Overall, this lens provides a high-quality manual focus experience, with an ideal rotational resistance, smooth movement, no play, and, when turned slowly, a slow rate of adjustment that facilitates precise manual focusing. As hinted, this focus ring has a variable adjustment rate based on the rotation speed. A full extent focus distance change requires 420° of rotation when turning the focus ring slowly. Turn the ring fast, and only 120° of rotation does the same. The rotation speed difference required to switch to the faster rate is significant enough to avoid inadvertent rate changes.

With a minimum focus distance of 8.7" (220mm), this lens has a useful, though unremarkable, 0.15x maximum magnification spec.

Model	Min Focus Distance "(mm)		Max Magnification
Sigma 20mm F1.4 DG HSM Art Lens	10.9	(277)	0.14x
Sigma 20mm F1.8 EX DG Lens	7.9	(201)	0.25x
Sigma 20mm F2 DG DN Contemporary Lens	8.7	(220)	0.15x
Sigma 24mm F2 DG DN Contemporary Lens	9.6	(245)	0.15x
Sigma 24mm F3.5 DG DN Contemporary Lens	4.3	(108)	0.50x
Sigma 35mm F2 DG DN Contemporary Lens	10.6	(270)	0.18x
Sigma 45mm F2.8 DG DN Contemporary Lens	9.4	(240)	0.25x
Sigma 65mm F2 DG DN Contemporary Lens	21.7	(550)	0.15x
Sigma 90mm F2.8 DG DN Contemporary Lens	19.7	(500)	0.20x
Sony FE 20mm F1.8 G Lens	7.1	(180)	0.20x
Sony FE 24mm F2.8 G Lens	7.1	(180)	0.19x
Sony FE 40mm F2.5 G Lens	9.8	(250)	0.23x
Sony FE 50mm F2.5 G Lens	12.2	(310)	0.21x
Tamron 20mm f/2.8 Di III OSD Lens	4.3	(109)	0.50x

A subject measuring approximately 7.7 x 5.13" (196 x 131mm) fills a full-frame imaging sensor at this lens's minimum focus distance.

The USPS love stamps shared above have an image area that measures 1.05 x 0.77" (26.67 x 19.558mm), and the overall individual stamp size is 1.19 x 0.91" (30.226 x 23.114mm).

The horse's eye in the image below was near lens's minimum focus distance.

Need a shorter minimum focus distance and higher magnification? Mount an extension tube behind this lens to significantly decrease and increase those respective numbers (likely only a short extension tube would retain focus in front of the lens). Extension tubes are hollow lens barrels that shift a lens farther from the camera, allowing shorter focusing distances at the expense of long-distance focusing. Electronic connections in extension tubes permit the lens and camera to communicate and otherwise function normally. As of review time, Sigma does not publish extension tube specs or manufacture these items, but third-party Sony-compatible extension tubes are available.

This lens is not compatible with Sigma teleconverters.

Build Quality & Features

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"I series" represents the build characteristics and styling of the lens.

"All I series lenses have an all-metal construction. The precision-cut aluminum parts not only give the barrel a sleek, stylish finish, but provide superb durability that improves the quality of the entire product. Metal materials are also used in internal structures that slide with the operation ring for added robustness. These high-precision components crafted with SIGMA's cutting-edge metalworking technology are also used in SIGMA's cine lens line-up for professional cinematographers and provide a tactile, ergonomic feel that make the lens a pleasure to use. The cover ring between the focus ring and the aperture ring has hairline processing that is also used for the rear cylinder of the Art line. This covering functions as a finger hold when attaching or detaching the lens." [Sigma]

While Sigma references this product as included in the "I series", the product name and lens graphics bear no mention of this designation. Regardless, Sigma's above description is accurate. This is a quality-constructed lens.

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While many current lens designs feature smooth lens barrels, this one design takes the opposite direction. Gear-like ribs stand out on the focus and aperture rings, and the cold, solid feel of metal is built in. The look and feel of this lens are different from many other lenses, but this is still a great look and feel.

I appreciate that Sigma provides an AF/MF switch on the compact I series lenses. With a relatively small space available for this switch, Sigma logically opted to rotate the conventional switch orientation by 90°, allowing a relatively large switch to fit nicely into a compact design. The AF/MF switch clicks assuredly into position, with a white background showing when the switch is in the AF position.

Sigma states, "Mount with dust- and splash-proof structure" from a weather sealing perspective. There is a gasket seal on the mount of this lens, but the "Mount with" part leaves us wondering about the rest of this lens's sealing.

Sigma I series lenses are compatible with in-camera lens aberration corrections when used on cameras supporting this feature.

The Sigma 20mm F2 DG DN Contemporary is a compact lens and, despite the metal construction, it is lightweight for this lens class. Carry this lens all day without being burdened.

Model	Weight oz(g)		Dimensions w/o Hood "(mm)		Filter	Year
Sigma 20mm F1.4 DG HSM Art Lens	33.5	(950)	3.6 x 5.1	(90.7 x 129.8)		2015
Sigma 20mm F1.8 EX DG Lens	18.4	(520)	3.5 x 3.4	(89.0 x 87.0)	82
Sigma 20mm F2 DG DN Contemporary Lens	13.1	(370)	2.8 x 2.9	(70.0 x 72.4)	62	2022
Sigma 24mm F2 DG DN Contemporary Lens	12.9	(365)	2.8 x 2.8	(70.0 x 72.0)	62	2021
Sigma 24mm F3.5 DG DN Contemporary Lens	7.9	(225)	2.5 x 2.0	(64.0 x 50.8)	55	2020
Sigma 35mm F2 DG DN Contemporary Lens	11.5	(325)	2.8 x 2.7	(70.0 x 67.4)	58	2020
Sigma 45mm F2.8 DG DN Contemporary Lens	7.6	(215)	2.5 x 1.8	(64.0 x 46.2)	55	2019
Sigma 65mm F2 DG DN Contemporary Lens	14.3	(405)	2.8 x 3.0	(72.0 x 76.7)	62	2020
Sigma 90mm F2.8 DG DN Contemporary Lens	10.4	(295)	2.5 x 2.4	(64.0 x 59.7)	55	2021
Sony FE 20mm F1.8 G Lens	13.2	(373)	2.9 x 3.3	(73.5 x 84.7)	67	2020
Sony FE 24mm F2.8 G Lens	5.7	(162)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Sony FE 40mm F2.5 G Lens	6.1	(173)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Sony FE 50mm F2.5 G Lens	6.1	(174)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Tamron 20mm f/2.8 Di III OSD Lens	7.8	(221)	2.9 x 2.5	(73 x 63.5)	67	2019

For many more comparisons, review the complete Sigma 20mm F2 DG DN Contemporary Lens Specifications using the site's lens specifications tool.

Did you notice how similar the Sigma DG DN Contemporary Lenses are in size? Here is a visual comparison of the four f/2 models:

Positioned above from left to right are the following lenses:

Sigma 20mm F2 DG DN Contemporary Lens
Sigma 24mm F2 DG DN Contemporary Lens
Sigma 35mm f/2 DG DN Contemporary Lens
Sigma 65mm F2 DG DN Contemporary Lens

The same lenses are shown below with their hoods in place.

Use the site's product image comparison tool to visually compare the Sigma 20mm F2 DG DN Contemporary Lens to other lenses.

A small lens gets narrow filter threads, and this lens's 62mm thread diameter is small. Small filters are convenient to pack and inexpensive to purchase. While the 62mm filter size is not especially popular, Sigma uses the same thread size in the Sigma 24mm F2 DG DN Contemporary Lens and Sigma 65mm F2 DG DN Contemporary I series lens.

The Sigma petal-type LH656-03 lens hood is included in the box. Designed to physically match the lens body, this hood has a solid, ribbed (inside and out) metal construction. Hoods built for prime lenses, vs. zoom lenses, can be tuned to a single focal length's angle of view, and this hood provides good protection from bright flare-inducing light and from impact.

Sigma does not include a case in the box with this lens.

Along with Sigma's standard (nice) center- and side-pinch lens cap, this lens ships with a nice aluminum magnetic cap. Snapping into place, the magnetic cap is easy to install, and it stays firmly in place.

Unfortunately, there is no provision to grip the center of the cap, and with inadequate space provided inside the hood to grasp the cap's edges, the hood must be removed to get the cap off. That was enough of a disadvantage for me to put the metal cap back in the box. If you leave your hood in the box (not recommended), you'll love the magnetic lens cap. The optional Sigma CH-11 Magnetic Cap Holder provides a simple method of attaching the lens cap to a camera bag, etc., via a carabiner.

Price, Value, Compatibility

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Sigma's name has become synonymous with good value, and Sigma's I series lenses continue that legacy. This lens is an outstanding performer, is strongly constructed, incorporates a great design, and is affordable.

The "DN" in the name indicates that this lens was designed for short flange mirrorless cameras. The Sigma 20mm F2 DG DN Contemporary Lens is available in Sony E-mount, compatible with both full-frame (indicated by "DG") and APS-C sensor format models, and is also available in Leica L-mount.

"Made in Japan" craftsmanship. "Every single lens undergoes SIGMA's proprietary MTF measuring system 'A1'". Sigma provides a 1-year limited warranty, and Sigma USA provides a limited 3-year warranty extension.

The reviewed Sigma 20mm F2 DG DN Contemporary Lens was on loan from Sigma Corporation of America.

Alternatives

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The first lens I was anxious to compare the Sigma 20mm F2 DG DN Contemporary Lens to is the impressive Sony FE 20mm F1.8 G. Right out of the name we can discern that the Sony lens has a 1/3 stop aperture advantage.

In the image quality comparison with wide-open apertures, the two lenses appear similarly sharp. The combination of considerable barrel distortion along with the modestly higher resolution a1 vs. the a7 III test cameras distorts this comparison somewhat. The geometric distortion advantage is a big one for the Sony lens. With the test results equalized at f/2, the Sony lens seems slightly sharper. The Sigma lens shows slightly fewer flare effects in the sun test. The Sony lens shows less color separation, including less lateral CA and less spherical aberration.

The Sigma 20mm F2 DG DN Contemporary Lens vs. Sony FE 20mm F1.8 G Lens comparison shows the two lenses with essentially identical weights. The Sigma lens is modestly smaller. The Sony lens has a smooth engineering plastic exterior barrel, while the Sigma lens features a metal exterior, including the hood. The Sigma lens is better suited to a video rig. The Sony lens has a programmable AF stop button, has a higher maximum magnification (0.20x vs. 0.15x), utilizes larger but more common filters (67mm vs. 62mm), and has a moderately higher price.

A friend suggested I share the Sigma 20mm F1.8 EX DG Lens comparison. While in name this lens appears as comparable as the Sony lens just discussed, the image quality comparison eliminates this contender. This comparison serves as a reality check for how great the latest lenses are.

FWIW, here is the Sigma 20mm F2 DG DN Contemporary Lens vs. Sigma 20mm F1.8 EX DG Lens comparison from a specifications standpoint.

If 24mm works for your application, the sibling Sigma 24mm F2 DG DN Contemporary Lens is worthy of comparison. In name, these two lenses are differentiated by a single digit, and from physical and performance standpoints, the differences seem even less.

In the image quality comparison, the 24mm lens appears slightly sharper in the corners. The 24mm lens has slightly less peripheral shading, including when stopped down.

Looking at the specifications, the Sigma 20mm F2 DG DN Contemporary Lens vs. Sigma 24mm F2 DG DN Contemporary Lens comparison shows no difference worth mentioning. These lenses are nearly identical. If the modest angle of view difference is not differentiating, the 24mm lens's nearly 10% lower price will probably be your decision-making factor.

Use the site's tools to create additional comparisons.

Summary

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The Sigma I series lens summaries are similar. If you are looking for a small, light, well-built, affordable lens that has a wide aperture, performs well, and covers the 20mm focal length, the Sigma 20mm F2 DG DN Contemporary Lens has your name on it.

This compact lens features metal interior and exterior construction, creating a solid build quality and increasing the fun factor for use. The 20mm focal length ensures plenty of opportunities for use, which increases the value of the lens. In addition, reviewing the results from this lens will bring a smile to your face as this lens produces razor-sharp imagery, including at f/2.

This lens's primary detractors are strong Peripheral shading (though this is normal for the lens class), some color separation, and strong barrel distortion.

The price is attractive for the overall quality and features of the Sigma 20mm F2 DG DN Contemporary Lens.