Tamron 20-40mm f/2.8 Di III VXD Lens Review

It was not until lens number 528 that the 20-40mm focal length range gained representation in the site's database.

With the 20-40mm f/2.8 Di III VXD Lens, Tamron keeps the focal length numbers nicely rounded to the tenth place. While this range is somewhat short (2x), a short range is not uncommon in ultra-wide-angle zoom lenses, this range is not available in most other full-frame lenses, the numbers in this range are extremely useful, and this lens has a size and weight advantages over others. Those looking for a modestly-wide-angle focal length range in a lightweight, compact, well-designed, high-performing, and affordable package should consider adding the Tamron 20-40mm f/2.8 Di III VXD Lens to their kit.

Focal Length Range

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Focal length drives subject distance choices, which determine perspective, and the focal length range is the first consideration for zoom lens selection.

This is the first 20-40mm lens available in a Sony E-mount (or Canon or Nikon mounts, though Pentax makes one for their K mount), but this relatively short range makes many popular prime lens focal lengths available without a lens change while enabling a compact, lightweight design.

Ultra-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. The 20mm focal length qualifies for this use. This angle of view allows a lot of subject in the frame despite a short working distance and is notably able to give the viewer a sense of the presence in the images.

On the other end, 40mm provides a normal angle of view that invites a subject distance creating a natural perspective, still making the viewer feel present in the scene. This focal length is wide enough to capture the scene but not so wide that people and other subjects are readily distorted by the close perspective invited by ultra-wide angles.

It is often easy to sneaker zoom to the right distance to get the ideal 20-40mm subject framing.

The 20-40mm angle of view is ideal for "scapes", including landscapes, nightscapes, cityscapes, buildingscapes, roomscapes, etc.

The 20-40mm range is ideal for photographing people, including yourself. This range is great for environmental photos of individuals and groups captured at a wide range of locations, from big scenic landscapes to birthday parties in small rooms. The long end is optimal for tighter portraits, including full and 3/4-body images still showing a pleasing perspective.

This is a great wedding lens.

Photographing architecture? Especially the 20mm end is a great choice for that pursuit.

While the 20mm angle of view is rather wide for use as a general-purpose lens, having the zoom range extend to 40mm makes this lens a great choice for that use. Use this lens to capture a day of family holiday festivities or other indoor and outdoor activities. This is a fun lens to carry around with a creative purpose. The 20-40mm range is a great choice for travel and street photography, and it can capture unique perspectives on sports.

Videographers will find a host of uses for this range, including vlogging.

The following images illustrate the full-frame 20-40mm focal length range:

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APS-C sensor format cameras utilize a smaller image circle than full-frame models, framing a scene more tightly. 1.5x is the angle-of-view equivalence multiplier for Sony APS-C cameras, creating a 30-60mm full-frame angle-of-view equivalent. This range gives up ultra-wide uses but nicely covers the standard range, increasing the portrait, products, and other longer distance needs.

Max Aperture

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The f/2.8 in the name refers to the maximum aperture, the ratio of the focal length to the entrance pupil diameter, available in this lens. The lower the aperture number, the wider the opening, and the more light the lens can deliver to the imaging sensor. Each "stop" in aperture change (full stop examples: f/2.8, f/4.0, f/5.6) increases or decreases the amount of light by a factor of 2x (a substantial amount).

The additional light provided by wider aperture lenses permits sharp images of subjects in motion, with the camera handheld in lower light levels, and with lower (less noisy) ISO settings. In addition, increasing the aperture opening provides a shallower DOF (Depth of Field) that creates a stronger, better subject-isolating background blur (at equivalent focal lengths). Often critical is the improved low-light AF performance availed by a wide-aperture lens.

A narrow aperture's advantages are related to (often significantly) reduced lens element size, including smaller overall size, lighter weight, and lower cost. Everyone loves those attributes.

As of review time, few zoom lenses have a maximum aperture opening wider than this one, and a wide aperture is a big feature advantage this lens holds. Despite that advantage, the just-mentioned potential disadvantages do not show up in this design. This is a small, light, and affordable lens with a wide f/2.8 aperture available over the entire range. Perfect.

These examples illustrate the maximum blur this lens can create:

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Interesting here is that the background is strongly blurred despite the low magnification of 20mm rendering the background details small in size. The short 20mm minimum focus distance is responsible for that aspect.

Image Stabilization

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The Tamron 20-40mm f/2.8 Di III VXD Lens does not feature image stabilization. Omitting the optical stabilization system reduces the size, weight, complexity, and cost. However, image stabilization is a useful feature.

Sony addresses that omission with Steady Shot IBIS (In-Body Image Stabilization) in their Alpha cameras. In addition to reducing camera shake, the stabilized imaging sensor provides a still viewfinder image, enabling careful composition. Furthermore, sensor-based AF takes advantage of the stabilized view for improved accuracy.

With no IS switch on the lens, the camera menu must be used to enable or disable IBIS or check the current settings. This extra step is a slight impediment to working quickly, going from tripod mounted to handholding, for example.

Image Quality

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You are probably getting tired of hearing about this lens's compact size, light weight, and affordable cost, but a design optimized for those factors can affect image quality. Asking for the f/2.8 results to be sharp seems like a stretch.

The good news is that this lens produces sharp f/2.8 center-of-the-frame results. The 20mm end results are extremely sharp, with a slight sharpness decline over the focal length range. 40mm results are still looking good but not quite as good as the 20mm results.

In general, lenses become sharper as they are stopped down one or two stops from their wide-open apertures. Stopping this lens down to f/4 results in no visible sharpness improvement at the wide end (where no improvement is needed), and the small improvement showing at the long end brings the results up to match the 20mm f/2.8 results.

Often, subjects are not placed in the center of a composition. In the periphery of the image circle, where light rays are refracted to a stronger angle than in the center, lenses typically show decreased sharpness, and this one shows a gradual decline from the center to the corner.

At the wide end of the focal length range, the f/2.8 image corners show only mild sharpness degradation for excellent performance. The f/2.8 corners from the longer focal length range are softer.

Stopping down improves corner sharpness. At the wider end, the stopping down primarily removes peripheral shading, increasing the contrast of already good performance. At the longer end, corner sharpness improves steadily through f/5.6, where corner performance is decent.

Next up is 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. Images from most cameras require some level of sharpening, but too-high sharpness settings are destructive to image details and hide the deficiencies of a lens.

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Overall, those results look great. The 40mm wide-open results are quite good, but a one-stop narrower aperture produces excellent sharpness.

Next, we'll look at a series of comparisons showing 100% resolution extreme corner crops captured and processed identically to the above center-of-the-frame images. The lens was manually focused in the corner of the frame to capture these images. The tree bark images are from the bottom left, and the other results are from the top left.

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The wide-open 20mm results are quite good, the 28mm f/2.8 results are close to the 20mm results, and the 40mm extreme corners are slightly soft. Stopping down to f/4 brings an increasing amount of improvement as the focal length is increased. The improvement at 20mm is primarily increased contrast from reduced peripheral shading. The 28mm results are close to the 20mm results, but the 40mm results show improved resolution through f/5.6.

Corner sharpness does not always matter, but it does matter for many uses, including landscape photography and architecture. When I'm photographing these subjects, I'm probably using f/8 or f/11 to obtain enough depth of field for in-focus corner details, and this lens performs superbly at these apertures. The corners are usually intentionally out of focus when shooting at wide apertures, and videos captured at typical wide-aspect ratios also avoid the use of corners.

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.

A lens is expected to show peripheral shading at the widest aperture settings when used on a camera that utilizes its entire image circle. Wide-angle, wide-aperture lenses tend to show strong peripheral shading wide open, and the just under 3 stops of shading at 20mm f/2.8 will be noticeable. By 24mm, the f/2.8 shading drops to just over 2 stops and to just under 2 stops at 28mm. The shading reduction slows through the rest of the focal length range.

To reduce corner shading, select a narrower aperture. At 20mm, f/4 reduces shading by about a stop to about 2 stops. With less shading to start with, the longer focal lengths show less reduction, to about 1.5 stops at f/4. The shading reduction ends at about f/5.6, with the remaining shading amounts ranging from just under 2 stops to about one stop.

APS-C format cameras using lenses projecting a full-frame-sized image circle avoid most vignetting problems. In this case, the just under one-stop of corner shading showing at f/2.8 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 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 set of worst-case examples. The images below are 100% crops from the extreme top left corner of Sony a1 frames showing diagonal black and white lines.

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Only black and white colors should be present in these images, with any additional colors indicating the presence of lateral CA. Especially for a zoom lens, these results are quite good.

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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This lens is producing obvious color differences in this test. While these effects are not unusual, a photo of a bride in a white wedding dress may have colors added to the out-of-focus areas of the dress, for example.

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 and ghosting effects in an image are variable, dependent 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. Additionally, flare and ghosting can impact AF performance.

"BBAR-G2 (Broad-Band Anti-Reflection Generation 2) Coating, TAMRON’s next-generation technology, suppresses ghosting and flare to enable the crisp and clear rendering of images." [Tamron]

The low 12-element count is also helpful in this regard. In our standard sun in the corner of the frame flare test, this lens's wide focal lengths produced some flare effects at narrow aperture, but overall, this lens performs well in this regard.

Flare effects can be embraced or avoided, or removal can be attempted. Unfortunately, removal is sometimes challenging, and in some cases, flare effects can destroy image quality. 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 that can be oriented either away from the center of the frame (external coma) or toward the center of the frame (internal coma). THe 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 images below are 100% crops taken from the top-left corner of Sony a1 images captured at the widest available aperture.

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While the results are not perfect at 20mm, they are good from a comparative standpoint. The 28mm results are not quite as good, but still decent. The 40mm results are a bit ugly.

This is a standard zoom lens, and the usual standard zoom lens geometric distortion description holds true, with the amounts being relatively modest in this case. This lens has modest barrel distortion at the wide end, transitions into negligible distortion at about 28mm, and has moderate pincushion distortion at the long end.

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. Due to the infinite number of variables present among available scenes, assessing the bokeh quality is considerably more challenging. Here are some f/11 (for diaphragm blade interaction) examples.

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The first example shows defocused highlights appearing normal. The second set of examples shows full images reduced in size and again looking normal.

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. That is the shape we're looking at here.

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The corner circles are not showing strong deformities. As the aperture narrows, the entrance pupil size is reduced, and the mechanical vignetting diminishes, making the corner shapes rounder. Note the shape blurs growing larger in the periphery vs. the center in the 20-28mm examples, likely indicating decreased depth of field in the outer portion of the image circle or field curvature.

A 9-blade count diaphragm will create 18-point sunstars (diffraction spikes) from point light sources captured with a narrow aperture. Generally, 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 decent stars, as illustrated below.

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The examples above were captured at f/16.

"The precision design features a generous arrangement special lens elements including four LD (Low Dispersion) lens elements that control light dispersion, and two GM (Glass Molded aspherical) lens elements which combine to produce high optical performance." [Tamron]

Like all others, this lens is not perfect. Expect 40mm results to be slightly soft at f/2.8, especially in the corners, to show some color blur and peripheral shading at the widest apertures, and some uncorrected geometric distortion may be apparent at the focal length extremities. However, the Tamron 20-40mm f/2.8 Di III VXD Lens makes an impression as a sharp lens that produces nice image quality.

Focusing

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Tamron 20-40mm f/2.8 Di III VXD Lens AF is driven by a VXD linear motor focus mechanism that checks all of the feature boxes.

Focusing is quiet, internal, and fast.

AF consistency and accuracy, the most important autofocus aspect, is excellent, and this lens locks focus on a contrasty subject in low light conditions.

The textured, ribbed focus ring is compact, but raised slightly from the lens barrel, making it easy to locate tactilely. While the focus ring performs well, it adjusts focus in slight steps, noticeable primarily when precise focusing is required.

Non-cinema lenses typically require refocusing after a focal length change. As illustrated in the 100% crops below, the reviewed lens does not fully exhibit parfocal-like characteristics. However, when focused at 40mm, zooming to wider focal lengths results in, at most, minor focus blur.

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If you adjust the focal length, re-establishing focus is usually a good idea.

By default, this lens has a non-linear rate of focus adjustment based on the ring's rotation speed. Turned slowly, the MF ring rotates 165° for a full-extent distance adjustment, while a fast turn does the same job in 50°.

However, the Tamron 20-40 focus ring is customizable.

Using the Tamron Lens Utility app (free) on a laptop (or mobile device using the mobile app), connected via the lens's USB Type-C port (the required USB cable is not included), linear MF is selectable, with 90, 180, 270, and 360° rotation angles optional. Reversing the focus ring direction is another available feature via the software.

It is normal for the scene to change size in the frame (sometimes significantly) as the focus is pulled from one extent to the other. This effect is focus breathing, a change in focal length resulting from a change in focus distance. Focus breathing impacts photographers intending to use focus stacking techniques, videographers pulling focus (without movement to camouflage the effect), and anyone critically framing while adjusting focus.

This lens produces a moderate change in subject size through a full-extent of focus distance adjustment.

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The Tamron 20-40mm lens does not have an AF/MF switch, requiring this frequently used camera setting to be changed via the menu system (or via a camera switch on some models).

With a minimum focus distance of 6.7" (170mm), this lens has a high 0.26x maximum magnification spec.

Model	Min Focus Distance "(mm)		Max Magnification
Canon RF 15-35mm F2.8 L IS USM Lens	11.0	(280)	0.21x
Sigma 14-24mm f/2.8 DG DN Art Lens	11.0	(280)	0.14x
Sigma 16-28mm F2.8 DG DN Contemporary Lens	9.8	(250)	0.18x
Sony FE 12-24mm F2.8 GM Lens	11.0	(280)	0.14x
Sony FE 16-35mm F2.8 GM Lens	11.0	(280)	0.19x
Sony FE PZ 16-35mm F4 G Lens	11.0	(280)	0.23x
Tamron 17-28mm f/2.8 Di III RXD Lens	7.5	(190)	0.19x
Tamron 20-40mm f/2.8 Di III VXD Lens	6.7	(170)	0.26x
Tamron 28-75mm f/2.8 Di III VXD G2 Lens	7.1	(180)	0.37x

At 20mm, a subject measuring approximately 4.8 x 3.2" (122 x 81mm) fills a full-frame imaging sensor at this lens's minimum MF distance. At 40mm, a 6.2 x 4.1" (157 x 105mm) subject does the same (0.20x maximum magnification).

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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).

While this lens produces sharp center of the frame details at minimum focus distance with a wide-open aperture, expect the image periphery to be soft due to field curvature. F/11 brings on increased depth of field that provides significant improvement in corner image quality.

The minimum focus distance is measured from the imaging sensor plane with the balance of the camera, lens, and lens hood length taking their space out of the number to create the working distance. At 40mm, there is plenty of working distance at the minimum focus distance but at 20mm, the plane of sharp focus is only about 0.9" (23mm) in front of the lens hood. Removing the hood adds some space, but the lens still affects the subject lighting in many scenarios.

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 by too much at the 20mm end). 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 function normally. As of review time, Tamron does not publish extension tube specs or manufacture these items, but third-party extension tubes are available.

This lens is not compatible with Tamron teleconverters.

Design & Features

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Tamron introduced a new design with the Tamron 50-400mm f/4.5-6.3 Di III VC VXD Lens, and the Tamron 20-40mm f/2.8 Di III VXD Lens gets the same.

I'll let Tamron introduce this design to you:

Engineered for Human Touch: The precision mechanics and engineering inside of the lens are encased in a robust barrel frame, contrasted by its texture, color tones, and lines have been engineered to create a warm, personable effect on the surface. That’s why the lens exterior in the new sculpted shape glows with a dignified presence, offering subtle changes in different lighting. Adding these subtle, human elements into the new series lenses is our way to instill in the photographer a sense of trust and reliability through the experience – the essentials for any long-term partnership." [Tamron]

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"New sculpted shape: The diameters of the zoom ring and focus ring have been enlarged, and the body areas around them have been slimmed down to give the lens a contoured profile that makes it easier to grip. This creates a comfortable, uneven shape that fits snugly and naturally in the hand."

"New design with improved texture and scratch resistance: Every individual part of the lens has been reexamined, right down to the fine details, resulting in a new design that updates both operability and the ergonomic considerations. The surface of the lens exterior is shiny black, much glossier than previous models. Improved abrasion resistance makes the lens harder to scratch and resists fingerprints. In addition, grip performance has been improved by increasing the number of protrusions in the striped pattern of the rubber ring. The smoothly curved, glossy surface of the brand ring creates a dignified appearance with a design that signifies functional beauty and high quality." [Tamron]

Tamron's new design is nice — it looks and feels good.

The 65° rotating zoom ring is compact but easy to use and ideally located (behind the focus ring). The lens extends 0.37" (9.3mm) when zoomed to 20mm. Both rings are smooth and easy to find tactilely.

There are no switches or buttons on this lens, but there is a USB-C port. Positive is that the lack of switches should mean increased reliability and decreased opportunity for dirt and moisture penetration.

"For greater protection when shooting outdoors, leak-resistant seals throughout the lens barrel help protect your equipment. Also, the Connector Port is the water-proofed USB Type-C variety."

"The front surface of the lens element is coated with a protective fluorine compound that is water- and oil-repellant. The lens surface is easier to wipe clean and is less vulnerable to the damaging effects of dirt, dust, moisture, and fingerprints." [Tamron]

The Tamron 20-40mm f/2.8 Di III VXD Lens is a lot about being compact and lightweight, and it is the smallest and lightest in this class list. This table will help with perspective in those regards.

Model	Weight oz(g)		Dimensions w/o Hood "(mm)		Filter	Year
Canon RF 15-35mm F2.8 L IS USM Lens	29.7	(840)	3.5 x 5.0	(88.5 x 126.8)	82	2019
Sigma 14-24mm f/2.8 DG DN Art Lens	28.1	(795)	3.3 x 5.2	(85.0 x 131.0)	n/a	2020
Sigma 16-28mm F2.8 DG DN Contemporary Lens	15.9	(450)	3.0 x 4.0	(77.2 x 100.6)	72	2022
Sony FE 12-24mm F2.8 GM Lens	29.9	(847)	3.8 x 5.4	(97.6 x 137.0)		2020
Sony FE 16-35mm F2.8 GM Lens	24	(680)	3.5 x 4.8	(88.5 x 121.6)	82	2017
Sony FE PZ 16-35mm F4 G Lens	12.5	(353)	3.2 x 3.5	(80.5 x 88.1)	72	2022
Tamron 17-28mm f/2.8 Di III RXD Lens	14.8	(420)	2.9 x 3.9	(73.0 x 99.0)	67	2019
Tamron 20-40mm f/2.8 Di III VXD Lens	12.9	(365)	2.9 x 3.4	(74.4 x 86.5)	67	2022
Tamron 28-75mm f/2.8 Di III VXD G2 Lens	19.1	(540)	3.0 x 4.6	(75.8 x 117.6)	67	2021

For many more comparisons, review the complete Tamron 20-40mm f/2.8 Di III VXD Lens Specifications using the site's lens specifications tool.

Here is a visual comparison:

Positioned above from left to right are the following lenses:

Tamron 20-40mm f/2.8 Di III VXD Lens
Tamron 17-28mm f/2.8 Di III RXD Lens
Tamron 28-75mm f/2.8 Di III VXD G2 Lens
Sony FE 16-35mm F2.8 GM Lens

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

Use the site's product image comparison tool to visually compare the Tamron 20-40mm f/2.8 Di III VXD Lens to other lenses.

Like many of Tamron's other mirrorless camera lenses, the 20-40 uses 67mm filters. This size commonality makes sharing effects filters such as circular polarizer filters easy. Note that a standard-thickness circular polarizer filter will slightly increase peripheral shading at wide angles. Therefore, a slim model such as the Breakthrough Photography X4 is recommended.

The Tamron HA062 Lens Hood is included in the box.

This plastic hood's petal shape is optimized to block as much light outside the utilized image circle as possible. Since zoom lens hoods must be tuned for the wide end of the zoom range, less than optimal protection is afforded at the long end. Still, this hood offers reasonable front element protection from bright lights and impact, including rain. The ribbed interior avoids internal reflections.

The petal design looks cool, and this shape makes installation alignment easy (simply align the small petal to the top). A release button is not featured on this hood.

No lens case is included in the box, but finding somewhere to stow this lens should not be challenging. Consider a Lowepro Lens Case or Think Tank Photo Lens Case Duo for a quality, affordable single-lens storage, transport, and carry solution.

Price, Value, Compatibility

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The Tamron brand is synonymous with good value, and the Tamron 20-40mm f/2.8 Di III VXD Lens delivers on that reputation, including a low price.

Tamron's Di III lenses are designed for use on mirrorless interchangeable lens cameras. The Tamron 20-40mm f/2.8 Di III VXD Lens is compatible with all Sony E-mount cameras, including full-frame and APS-C sensor format models.

"This product is developed, manufactured and sold based on the specifications of E-mount which was disclosed by Sony Corporation under the license agreement with Sony Corporation." [Tamron] I can't say how the license agreement impacts Sony Corporation, but we have some really nice third-party E-mount lenses available.

Tamron USA provides an impressively-long 6-year limited warranty.

The reviewed Tamron 20-40mm f/2.8 Di III VXD Lens was online-retail sourced.

Alternatives

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With no other 20-40mm lenses available, there are no direct alternatives to this lens, and the focal length range of even the closest alternatives is not so close. For example, the Tamron 17-28mm f/2.8 Di III RXD Lens shifts the focal lengths to considerably wider and shorter. Still, let's review the differences between these lenses.

In the image quality comparison, the 17-28 produces sharper corners in the overlapping range. The 20-40 has modestly less peripheral shading at 28mm f/2.8 and at 20mm with narrow apertures. The 17-28 also shows less geometric distortion in the shared range.

The Tamron 20-40mm f/2.8 Di III VXD Lens vs. Tamron 17-28mm f/2.8 Di III RXD Lens comparison shows the 20-40 slightly lighter and noticeably smaller. The 17-28 has a fixed external size. The 20-40 has a higher maximum magnification (0.26x vs. 0.19x), and it has a USB connection for focus ring customization and firmware updates. The 20-40 is modestly less expensive.

If we compare the Tamron 17-28, we should also review the Sigma 16-28mm F2.8 DG DN Contemporary Lens.

The image quality comparison shows the two lenses trading some advantages, but the Tamron lens is a bit sharper in the center of the frame in most overlapping focal length comparisons. The Tamron has less peripheral shading at f/2.8 and still less shading at 20mm with narrow apertures. The 20-40 also shows significantly less geometric distortion in the shared range.

The Tamron 20-40mm f/2.8 Di III VXD Lens vs. Sigma 16-28mm F2.8 DG DN Contemporary Lens comparison shows the 20-40 slightly lighter and noticeably smaller, especially when retracted at 40mm. The Sigma lens has a fixed external size. The 20-40 has a higher maximum magnification (0.26x vs. 0.18x), and it has a USB connection for focus ring customization and firmware updates. The Sigma lens has much wider angles of view, and the Tamron lens has considerably longer angles of view. The Tamron lens has a moderately lower price.

Relative to the last two lenses compared, the Sony FE 16-35mm F2.8 GM Lens covers a wider range of the Tamron lens's focal length range.

In the image quality comparison, the two lenses are similar at 20mm f/2.8. The Sony lens has a modest advantage at 24mm, a big advantage at 28mm, and a modest advantage at 35mm. The Tamron lens shows greater geometric distortion at the wide end, and the Sony lens has more distortion over much of the longer end.

The Tamron 20-40mm f/2.8 Di III VXD Lens vs. Sony FE 16-35mm F2.8 GM Lens comparison shows the Sony lens dimensionally larger and weighing nearly twice as much as the Tamron lens. The Sony lens has 11 aperture blades vs. 9 and uses 82mm filters vs. 67mm. The Sony lens has much wider angles of view, and the Tamron lens has modestly longer angles of view. Not easy to overlook is that the Tamron lens costs about 1/3 as much as the Sony lens.

Use the site's tools to create additional comparisons.

Summary

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The Tamron 20-40mm f/2.8 Di III VXD Lens is an interesting lens. It is compact, lightweight, affordable, nicely designed, and a good performer, including good image quality and a superb AF system. The 20-40mm focal length range is sometimes ideal, avoiding frequent lens changes.

Likely, that package would fit into your kit.