The Tamron 28-75mm f/2.8 Di III RXD Lens has been at the top of the best-selling lens list since it was introduced (minimally for well over a year) and it remained out of stock for a very long time. Why am I starting the Tamron 17-28mm f/2.8 Di III RXD Lens review with that statement? This is that lens in a different focal length range. The second member of Tamron's f/2.8 RXD lens trinity has similar appeal as the first and practically launched as a best-selling lens, ranked not far below its general-purpose sibling.
The Tamron 17-28mm f/2.8 Di III RXD Lens provides a very useful focal length range, one that matches perfectly with the 28-75mm lens, with a wide f/2.8 aperture available over the entire range enhancing that appeal. This is a compact lens in a very attractive package with a price that is equally attractively. Do you like fast, quiet, and smooth autofocus? This lens has that. Do you like sharp images? This lens also delivers in this regard.
Tamron's f/2.8 RXD lens lineup is taking shape and the fan base has been delighted and growing. If you have a Sony full frame or cropped (APS-C) format E-mount camera, the Tamron Di III RXD line is worth consideration.
The Tamron 28-75mm f/2.8 Di III RXD Lens does not have the widest-angles available in a general-purpose zoom lens and the Tamron 17-28mm f/2.8 Di III RXD Lens does not have the longest focal lengths available in an ultra-wide-angle zoom lens. However, the two match up perfectly with no overlap and no gap for size and economic efficiencies.
One of the first reasons to buy a lens or to select a lens for use is because the focal length or focal length range meets the needs of the subject being photographed. Lenses containing an ultra-wide-angle zoom focal length range are extremely popular and for a good reason: there are a huge number of subjects that are best captured with this range.
Lenses in this category vary somewhat in their focal length ranges and 16mm has been my personal benchmark for comparing ultra-wide-angle options. This Tamron lens gives us 17mm on the wide end, a really wide-angle of view slightly (but noticeably) narrower than 16mm. On the long end, 35mm has been my benchmark and this lens falls noticeably short of that mark though carrying the previously-mentioned 28-75mm lens completely eliminates that shortcoming.
When you cannot get any farther away from your subject but still need to get a wide-angle of view in the frame, you want an ultra-wide-angle lens. Better still is to be able to choose an ultra-wide-angle for perspective reasons. An ultra-wide-angle lens has the capability, via perspective, of making a foreground object (ideally something interesting or attractive such as a flower or rocks) appear large and emphasized in relation to a distant yet potentially in-focus background with a vast amount of background in the frame and with subjects in the background rendered relatively small (like the sun in the example above). To the vast amount of background point, especially careful attention must be paid to ultra-wide-angle composition and hopefully the background is as attractive as the foreground. I generally find excellent ultra-wide compositions more challenging to create than normal or telephoto compositions, but when the right scene is found, ultra-wide results are tremendously rewarding.
The foreground emphasis with background inclusion capability fits especially well with landscape photography and this entire focal length range is perfect for that use. Start looking for a beautiful patch of flowers in front of a large mountain range (perhaps with a lake between them for an additional layer of interest) to utilize the ultra-wide-angle concepts just discussed. Or zoom to 28mm to take in a smaller angle of view, keeping distant subjects (such as mountains) larger in the frame. Also, try using a wide-open aperture with that close subject, letting the background go out of focus and drawing more emphasis on the foreground subject.
The 28mm end of this focal length range is easy to compose with. This also-useful focal length shows a natural perspective, allowing the viewer to feel part of the scene.
While a close-up wide-angle perspective can look amazing in a landscape scene, it is generally to be avoided when a person is the primary subject. What you do not (usually) want to appear large in the foreground of your ultra-wide composition is a person's nose. We do not typically look at a person from really close distances and if we do, that person becomes uncomfortable with us being in their personal space (and even more so when a camera is in hand). When we look at photos of people captured from very close distances, certain body parts (usually the nose) start to look humorously (to some) large. Unique portrait perspectives can be fun, but this technique should not be overused as it quickly gets old. Get the telephoto lens out for your tightly-framed portraits.
However, that does not mean wide-angle focal lengths are not a good choice for photographing people. Simply move back and include people in a larger scene, creating environmental portraits. The 28mm focal length can work for full-body portraits and this focal length range also nicely handles small up to very large groups. Note that group photography requiring an ultra-wide-angle focal length to fit everyone in the frame often leaves those in the front row appearing considerably larger than those in the back row. Back up or move the subjects back to reduce the multi-row perspective issue.
The 17-28mm focal length range is a great option for the wide work at weddings, family gatherings, and at other events as well as for photojournalism and sports photography needs. This lens can also be used overhead, to photograph over crowds such as those arriving on-field after football games.
Many of the just-discussed uses happen at a venue that itself is worthy of being photographed. Wide-angles make interior spaces, from houses to vehicles, look large and allow for illustrative composition even when working space is limited. This focal length range is important for architecture.
When photographing architecture, a level camera is often desired to keep walls and the sides of buildings straight/vertical in the frame, avoiding converging lines. However, it is not always possible, affordable, or convenient to get the camera to a height that permits the desired framing with a level camera. This is especially common when photographing the exterior of buildings from ground level. A tilt-shift lens is the ideal choice for this situation, but an ultra-wide-angle lens can also get the job done. Simply set up the camera in a level position, zoom out until the building (or other subject) is contained in the frame, capture the image, and then crop away whatever is not desired in the frame, typically at the bottom, during post processing. Basically, having a lens that takes in wide angles of view can circumvent the need for a tilt-shift lens (with resolution loss from the cropping being a downside) or pixel-level-destructive perspective correction.
Directly related to architecture photography is real estate photography and that use has us circling back to include the landscape capabilities of this focal length range.
The landscape after dark, aptly described as nightscape, is a frequent use for the 17-28mm range. Also, count cityscapes on this lens' great uses list.
Do you like the looking upward into the woods with tree trunks converging into the center of the frame type of picture? This lens can do that. It is seldom that my pack does not have a lens covering this focal length range in it.
Following are examples of what this focal length range looks like on a full frame camera:
APS-C sensor format cameras utilize a smaller portion of the image circle and that means a scene is framed more tightly, with 1.5x being the full frame equivalent angle of view multiplier for Sony's lineup. On an APS-C body, this lens provides an angle of view equivalent to a 25.5-42mm lens on a full frame camera. While those with primarily wide-angle needs may find the 17-28mm range on a full frame camera to be ideal for general-purpose needs, the APS-C angle of view is more ideal for a majority of photographers. These cameras do not get the extreme wide-angle of views to work with, but the angle of views present are even better for portraiture and other images including people, for products, for what is encountered on the street, for sports, etc.
As of review time, very few zoom lenses have a maximum aperture opening wider than this one and a wide aperture is a big feature advantage this lens holds.
Wide apertures are useful for stopping action, both that of the subject and that of the camera, in low light levels while keeping ISO settings low. While having an f/2.8 aperture may not be a big advantage from ISO and shutter speed perspectives when photographing under bright light (daylight for example), the story is different in low light scenarios.
Wide apertures benefit AF systems, enabling them to work better in low light environments. Even when photographing under bright light conditions, wide apertures are useful for creating a strong background blur that makes a subject cleanly stand out, isolated from an even highly distracting background.
Here is an example of the maximum background blur this lens can produce:
A disadvantage of a wide aperture is the required increased in physical size of the lens elements. Those larger lens elements come with heavier weight and higher cost. This lens nicely side-steps those disadvantages.
This lens does not feature image stabilization and with a combination of wide-angle focal lengths and an f/2.8 aperture, it often does not need this feature. While image stabilization adds greatly to the versatility of a lens, it also adds size, weight, and cost while potentially compromising image quality and durability. With Sony's mirrorless cameras featuring IBIS (In Body Image Stabilization), the need for a lens to provide this feature is further diminished.
The Tamron 28-75mm f/2.8 Di III RXD Lens set the image quality expectations very high for the forming Di III RXD lens lineup. Does the Tamron 17-28mm f/2.8 Di III RXD Lens meet those expectations? Let's find out.
In the center of the frame, the Tamron 17-28mm f/2.8 Di III RXD Lens delivers great sharpness, referring to resolution and contrast, with a wide-open f/2.8 aperture. The center-of-the-frame results slowly get very slightly softer as the focal length increases, but the center of the frame is still very sharp at 28mm. Stopping a lens down one or two stops from wide-open usually results in sharper image quality but this lens is so sharp in the center at the wider angles that the difference made by stopping down to f/4 is barely recognizable and the difference is only slightly noticeable at the long end. At f/4, this lens is razor sharp.
Image quality typically degrades as the image circle's radius is traversed, meaning that corners are seldom rendered as crisply as the center of the frame. That said, this lens holds excellent image quality deep into the corners of the frame even at f/2.8. The primary improvement seen at narrower apertures is decreased peripheral shading.
Taking the testing outdoors, below you will find sets of 100% resolution center of the frame crops captured in uncompressed RAW format using a Sony a7R III. The images were processed in Capture One using the Natural Clarity method with the sharpening amount set to only "30" on a 0-1000 scale. Note that using even modestly-high sharpness settings are destructive to image details (creating fake sharpness) and hide the true characteristics of a lens.
Why are three sets of results provided for the 17mm focal length? Sometimes it requires less brain power to process an additional set of results than to select between them.
In some lens designs, the plane of sharp focus can move forward or backward as a narrower aperture is selected. This is called focus shift (residual spherical aberration or RSA), it is seldom (never?) desired, and I did not have that problem with this lens.
Next, we'll look at a comparison showing 100% extreme-top-left-corner crops captured and processed identically to the above center-of-the-frame images. These images were manually focused in the corner of the frame.
The extreme corners show a bit of softness with lateral CA being partially to blame and stopping down improves the other aspects affecting corner performance. For an ultra-wide-angle zoom lens, this performance is quite good.
Corner sharpness does not always matter but it does matter for many disciplines including landscape photography. When corner sharpness is important, I'm likely using an aperture narrower than f/5.6.
When used on a camera that utilizes a lens' entire image circle, peripheral shading can be expected, at least at the widest aperture settings. Wide-angle, wide-aperture lenses tend to show strong peripheral shading wide-open and the over-3.5-stops of shading in this lens' 17mm corners is relatively strong but normal. Increasing the focal length decreases the shading with nearly 2.5 stops showing in 28mm corners. Stopping down one stop reduces the shading by about 0.5-stops with slightly more reduction showing at the long end. Only slight vignetting reduction is achieved by using apertures narrower than f/4. Even at f/16, nearly 2-stops of shading remains in the 17mm corners and roughly 1.4-stops remain at the longer focal lengths.
One stop of shading is the amount often used as the visibility threshold, though subject details provide a widely-varying amount of vignetting discernability. Especially at 17mm, this lens exceeds that benchmark when stopped down. Vignetting can be corrected 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 showing in our vignetting test tool to determine if your subject (subject's face) will be darkened or if it will be emphasized by the darker periphery.
APS-C format cameras using lenses projecting a full-frame-sized image circle avoid most vignetting problems.
The effect of different colors of the spectrum being magnified differently is referred to as lateral (or transverse) CA (Chromatic Aberration). 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 greatest amount as this is where the greatest 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 though it is always better to not have the problem in the first place. Any color misalignment present can easily be seen in the site's image quality tool, but let's also look at a set of worst-case examples, 100% crops from the extreme top left corner of Sony a7R III frames showing diagonal black and white lines.
There should be only black and white colors in these images with the additional colors showing the presence of lateral CA. Usually, we see the colors aligning at a mid focal length and then the misaligned colors shifting sides. I didn't test the intermediate focal lengths, but it seems this lens has a modest and rather consistent amount of this aberration across the focal length range.
A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light, or 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 look for. Axial CA remains at least somewhat persistent when stopping down with the color misalignment effect increasing with defocusing while 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.
In the examples below, look at the fringing colors in the out of focus specular highlights created by the neutrally-colored subjects. Any color difference is being introduced by the lens.
At 17mm, the colors appear rather neutral. A slight color disparity becomes recognizable at 22mm and the 28mm results are ... quite colorful.
"The BBAR (Broad-Band Anti-Reflection) Coating applied to lens surfaces reduces ghosting and flare that are otherwise likely to occur when shooting against the sunset’s glow and other backlit situations." [Tamron USA] That coating along with a relatively low 13 element count (in 11 groups) produces excellent flare control. Even at f/16 with the sun in the corner of the frame, this lens shows very little flaring.
There are two lens aberrations that are particularly evident when shooting 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). 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). Remember that lateral CA is another aberration apparent in the corners.
The images below are 100% crops taken from the extreme top-left corner of a7R III frames.
While this lens does not produce the perfect pin-point stars in the corner of the frame, these results are quite good in comparison.
This lens has barrel distortion at the wide end that transitions into negligible distortion (at just longer than 17mm) and on into pincushion distortion at the long end. The amount of barrel distortion at 17mm is quite low in comparison to similar lenses and the amount of pincushion distortion increases to moderate at the long end. These amounts are normal for this class of lens. Most modern lenses have lens correction profiles available for the popular image processing software and distortion can be easily removed using these, but distortion correction is destructive at the pixel level as some portion of the image must be stretched or the overall dimensions must be reduced.
The blur and quality of blur seen in the out of focus portions of an image are referred to as bokeh. While wide-angle lenses are not the best suited for creating a strong blur, this lens' f/2.8 aperture gives it the ability to do so. Here are some 100% crop f/11 examples showing aperture blade interaction.
With the exception of a small number of specialty lenses, the wide aperture bokeh in the corner of the frame 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 corner of the frame, the shape is not round and that is the shape being seen here. The examples below are upper-left quarter of the frame crops reduced in size.
This lens' corner highlight shapes remain rather round and as the aperture narrows, the entrance pupil size is reduced with the mechanical vignetting absolving and the shapes becoming ideally round.
With a 9-blade count aperture, point light sources captured with a narrow aperture setting and showing a star-like effect will have 18 points. Wide aperture lenses tend to have an advantage in this regard and this lens is capable of producing beautiful stars.
Another example of this effect can be seen in the Acadia National Park sunset image shared at the beginning of the review.
This lens utilizes XLD (eXtra Low Dispersion) and LD (Low Dispersion) lens elements to reduce color fringing and chromatic aberrations.
This is an optically-strong-performing lens without consideration of its price and taking price into account, this is a remarkably-high-performing lens.
"The new 17-28mm zoom’s AF drive system is powered by the RXD (Rapid eXtra-silent stepping Drive) stepping motor unit that enables it to deliver high-speed, high-precision operation." "RXD uses an actuator to precisely control the rotational angle of the motor, allowing it to directly drive the focusing lens without passing through a reduction gear. A sensor that accurately detects the position of the lens enables high-speed and precise AF, which is ideal when shooting continually moving subjects or video." [Tamron USA]
Like its RXD-sharing 28-75mm sibling, the Tamron 17-28mm f/2.8 Di III RXD Lens quietly and smoothly autofocuses very fast.
Focusing is internal and it is consistently very accurate, a huge key for fully realizing a lens' image quality potential. FTM (Full Time Manual) focusing is supported in Sony's DMF (Direct Manual Focus) AF mode and this lens supports advanced AF features in compatible cameras including Hybrid AF and Eye AF.
This lens design places the focus ring behind the zoom ring. While this design is seldom (never?) my preference, it is a perfect design for making the focus ring easy to use, especially when using the lens handheld as the focus ring is at my fingertips when the mounted lens is balanced in my left hand. This nearly-flush-mounted focus ring is modestly-sized with a slightly grippy surface finish. The focus ring has a relatively light but adequate amount of resistance with no play.
As illustrated below, there is a modest amount of change in subject size (focus breathing) as focus is full-extent adjusted.
While a distance window is not provided, a focus distance meter shows in the lower portion of Sony's electronic viewfinders during manual focusing.
With a 7.5" (190mm) minimum focus distance (referred to as minimum object distance or MOD by Tamron), the Tamron 17-28mm f/2.8 Di III RXD Lens features a 0.19x maximum magnification. While the maximum magnification spec is not an eyebrow-raiser, 7.5" is very close and this lens' close focusing capabilities are good.
|Canon RF 15-35mm F2.8 L IS USM Lens||11.0"||(280mm)||0.21x|
|Canon EF 16-35mm f/2.8L III USM Lens||11.0"||(280mm)||0.25x|
|Sony FE 16-35mm f/2.8 GM Lens||11.0"||(280mm)||0.19x|
|Tamron 17-28mm f/2.8 Di III RXD Lens||7.5"||(190mm)||0.19x|
|Tamron 28-75mm f/2.8 Di III RXD Lens||7.5"||(190mm)||0.34x|
|Tokina 16-28mm f/2.8 AT-X Pro FX Lens||11.0"||(280mm)||0.19x|
Need a shorter minimum focus distance and greater magnification? A short extension tube mounted behind this lens should provide a very significant improvement and third-party Sony extension tubes are available.
This lens is not compatible with Tamron teleconverters.
This lens shares many of the 28-75mm RXD lens design traits as seen in this comparison image.
This lens looks great and it feels great in hand.
The light weight and polycarbonate exterior design are not going to provide reassurance of a rugged design like a cold metal lens, but this still feels like a high-quality product. Tight tolerances on moving parts add some assurance that this lens has been carefully designed and that modern construction methods were utilized. The lens has a very nicely-smooth narrow shape and the matte/satin black finish along with the engraved white lettering with a modern, attractive font style looks great. The "Luminous Gold" ring is once again featured and it still appears very silver-like to me. White gold perhaps? Regardless, it is a nice aesthetic touch.
The rubber-coated zoom ring rises very slightly from the barrel and is very smooth with no play. This lens does not change overall size while zooming but the inner lens assemblies move as seen in the product images shared above. The zoom ring logically turns in the same direction as Sony's zoom lenses, increasing focal length while being rotated clockwise (same as Nikon, opposite of Canon).
This lens has exactly 0 buttons and switches. The AF/MF button is one that I often miss and having to use a menu option (programmed to a custom button) for this commonly-used feature is sometimes annoying. Positive is that the lack of switches should mean increased reliability and decreased the chance for dirt and moisture penetration.
This lens features a "Moisture-Resistant Construction."
"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 USA] Even an oily fingerprint easily wipes away and this feature is especially appreciated if the lens gets dirty in the field.
Tamron claims that this lens "... is compatible with many of the advanced features that are specific to mirrorless cameras." One such feature is camera-initiated lens firmware updates. The installation process is similar to that of the Sony camera firmware updates, utilizing the provided computer-based software to manage the process via a direct-to-camera USB connection with no USB Tap-In console required.
I often complain about the lack of finger space Sony provided between the lens and grip in their review-time-current mirrorless cameras including the a7R IV. While the first joint on my right hand's middle finger still impacts the lens body, becoming red and slightly sore when holding this lens in shooting position for relatively long periods of time, the relatively narrow lens body means that the pressure is not as bad as with Sony's larger lenses.
From a size and weight perspective, this lens is in a class of its own.
|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|
|Canon EF 16-35mm f/2.8L III USM Lens||27.9||(790)||3.5 x 5.0||(88.5 x 127.5)||82||2016|
|Sony FE 16-35mm f/2.8 GM Lens||24.0||(680)||3.5 x 4.8||(88.5 x 121.6)||82||2017|
|Sony FE 16-35mm f/4 ZA OSS Lens||18.3||(518)||3.1 x 3.9||(78.0 x 98.5)||72||2014|
|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 28-75mm f/2.8 Di III RXD Lens||19.4||(550)||2.9 x 4.6||(73.0 x 117.8)||67||2018|
|Tokina 16-28mm f/2.8 AT-X Pro FX Lens||33.5||(950)||3.5 x 5.2||(90.0 x 133.3)||n/a||2011|
For many more comparisons, review the complete Tamron 17-28mm f/2.8 Di III RXD Lens Specifications using the site's lens specifications tool.
Consider the difference in size and weight this lens makes in a kit.
Positioned above from left to right are the following lenses:
The same lenses are shown below with their hoods in place.
Use the site's product image comparison tool to visually compare the Tamron 17-28mm f/2.8 Di III RXD Lens to other lenses.
A kit with the Tamron 17-28 and 28-75 lens doubles the difference between the Sony near-equivalents. Those moving to mirrorless lenses for the small size and lighter weight take notice.
With a smooth, narrow, and lightweight design, this lens is a pleasure to carry and use for even long periods of time. I've carried the 17-28 lens over many miles in the last few months and barely knew it was there.
The medium-sized 67mm filter threads mean that filters for this lens are not too expensive. Also positive is that this is a common filter size, increasing the potential for filter sharing — notably including among Tamron's RXD lenses. Note that using a standard thickness circular polarizer filter will noticeably increase peripheral shading at 17mm. A slim model such as the B+W XS-Pro or Breakthrough X4 is highly recommended.
We can always count on Tamron to include the lens hood in the box with this lens model getting the HA046 lens hood (logically adding an "H" for hood to the front of the lens' model number "A046"). This nice-looking semi-rigid plastic hood is not big but it definitely provides some protection from impact and from flare-inducing bright lights. The hood bayonet-mounts and lacks a release button. Use the hood and reversed does not count.
A lens case is not included with this lens. Lowepro's Lens Cases are a favorite for a quality, affordable single-lens storage, transport, and carry solution. Most lens caps provided today work very well, but Tamron's lens caps have long been great.
As you likely have discerned by now, this lens is a bargain. The feature set combined with great image quality would make this lens a good value even at a considerably higher price.
What does "Di III" mean? Tamron's Di III lenses are designed for use on mirrorless interchangeable lens cameras. The Tamron 17-28mm f/2.8 Di III RXD Lens specifically is compatible with all Sony E-mount cameras, including both full frame and APS-C sensor format models.
At this point in a review, I always provide a disclaimer regarding potential compatibility issues with third-party lenses. That Sony has worked closely with third parties reduces the risk to those purchasing this lens. That the firmware for this lens can easily be updated through compatible cameras further reduces risk.
Tamron USA provides a significant 6-year limited warranty and Tamron Europe's limited warranty is an also-long 5 years. Those warranty durations should help alleviate any build quality concerns.
The reviewed Tamron 17-28mm f/2.8 Di III RXD Lens was on loan from Tamron USA. Unfortunately, they requested the lens back after a few months.
Those considering the purchase of this lens have (or are considering adding) a Sony camera in their kit and the nearest equivalent Sony lens is the FE 16-35mm f/2.8 GM Lens. This is an excellent lens that I currently own.
In the image quality comparison, I'm going to have a hard time convincing you that the Sony is worth the additional cost. At f/2.8, the Sony lens is sharper in the center of the frame and the Tamron has the edge in most corners. Stopped down, the differences fade. The Sony lens has less peripheral shading at f/2.8 at the long end of the comparable range and has slightly less over the entire range when stopped down. The Tamron lens has less distortion at 17mm than the Sony lens has at 16mm but the two lenses should appear more similar in an equal 17mm comparison.
Looking at the specs and measurements, the Tamron 17-28mm f/2.8 Di III RXD Lens vs. Sony FE 16-35mm f/2.8 GM Lens comparison shows the Sony lens weighing and measuring considerably more than the Tamron lens. The difference is significant and very noticeable. In addition to being larger, the Sony lens extends when zooming. Along with the smaller size comes smaller filter threads for the Tamron lens, 67mm vs. 82mm. The Sony lens has 11 aperture blades vs. 9. The Tamron lens focuses much closer (7.5" vs. 11.2" / 190mm vs. 280mm) but the two lenses share the same maximum magnification spec. The Sony lens has the noticeably longer focal length range and this lens' switches can be a decision factor. The Tamron lens costs far less than the Sony lens.
I rarely suggest buying a specific camera brand so that a lens from a different manufacturer can be used but this is a scenario where that could make sense. I could justify selecting a Sony camera so that the Tamron 17-28mm f/2.8 Di III RXD Lens could be used. This lens is an excellent value.
As with the Tamron 28-75mm f/2.8 Di III RXD Lens, the 17-28 delivers image quality comparable to the best-in-class lenses, yet this lens is far smaller, much lighter, and costs significantly less than the premier brand lens options. This lens' light weight does not exude rugged build quality confidence, but it seems nicely built with tight tolerances and the very long warranty indicates that Tamron expects the lens to endure the test of time.
The Tamron 17-28mm f/2.8 Di III RXD Lens maintains the spirit of mirrorless interchangeable lens cameras, providing very impressive image quality from a small-sized and lightweight package. The low price of this lens does not veer from the mirrorless spirit and perhaps exceeds it. Tamron's first Di III RXD lens set the expectations high and I'm not at all surprised that the second RXD lens has joined the best-seller list. It will likely be there for a long time.
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