Tamron 28-75mm f/2.8 Di III RXD lens
Tamron’s first dedicated FE lens is a very nice bit of gear at a modest price. It’s relatively compact and light for a standard zoom lens with an f/2.8 constant maximum aperture.
This makes it a good choice for travellers and everyday photographers who are looking for a relatively small and light ‘take everywhere’ standard zoom and it’s well suited to event photography and holiday shooting.
Officially launched at the end of April, Tamron’s 28-75mm f/2.8 Di III RXD (Model A036) lens is designed specifically for the Sony α7 range of full-frame mirrorless cameras and is the first of its type from a third-party manufacturer. Spanning a moderate wide-angle to portrait focal length range, the new lens has a constant f/2.8 maximum aperture that allows depth of field control and useful low-light performance. No stabilisation is included, since sensor-shift stabilisation is built into all Sony E-mount cameras.
Side view of the Tamron 28-75mm f/2.8 Di III RXD lens without end caps and lens hood. (Source: Tamron.)
The optical design of this lens uses 15 elements in 12 groups and includes a special XLD (eXtra Low Dispersion) element, one LD (Low Dispersion) element, one GM (Glass Moulded Aspherical) element and two hybrid aspherical lens elements. Together, they minimise common aberrations and reduce the overall lens size.
The optical diagram for the Tamron 28-75mm f/2.8 Di III RXD lens showing the positions of the exotic lens elements. (Source: Tamron.)
Tamron’s BBAR (Broad-Band Anti-Reflection) coating is used to suppress internal reflections throughout the entire zoom range, even in backlit conditions. The nine-blade circular diaphragm ensures soft bokeh at wide aperture settings plus a clear and sharp image when stopped down.
Environmental seals are located at the lens mount area and other critical locations to prevent ingress of moisture and dust and provide an additional layer of protection when shooting outdoors under adverse weather conditions. The front surface of the lens is coated with a fluorine compound that has excellent water- and oil-repellant qualities, making the lens surface easy to wipe clean and less vulnerable to the damaging effects of dirt, moisture or oily fingerprints.
A new RXD (Rapid eXtra-silent-stepping Drive) system promises fast and precise autofocus performance with near-silent operation, making it ideal for video and wedding shooters. With a minimal focus of 19 cm at the 28mm and 39 cm at 75mm, the lens can be used for close-up shots with the f/2.8 maximum aperture enabling depth of field control with attractive bokeh.
The 28-75mm f/2.8 Di III RXD lens is supplied with the normal front and rear dust caps plus a petal-shaped lens hood that reverses over the lens barrel for storage. We reviewed the lens on a Sony α7S camera.
Who’s it for?
Standard zoom lenses are popular for their general versatility. Most photographers include one in their kits for everyday use. The E-mount makes this lens specific to Sony’s E-mount cameras and, while it can be fitted to cameras with APS-C sized sensors, a similar focal length range would be better addressed for those cameras by Sony’s much cheaper (but significantly slower) E-Mount PZ 16-50mm f/3.5-5.6 OSS lens.
The RXD stepping motor’s near silent operation makes this lens ideal for recording movie clips as well as shooting stills in situations where noise is prohibited (such as wedding ceremonies). Even in near silent conditions, little or no noise can be heard on video soundtracks.
Compared with Sony’s offerings, the Tamron lens sits right in the middle of the zoom range. Its 28-75mm zoom is slightly longer but not quite as wide as the FE 24-70mm f/2.8 G Master lens (SEL2470GM), which we reviewed in June 2016. However, it’s more than 300 grams lighter than that lens and less than half its price.
Size-wise, the Tamron lens has a similar diameter to the Sony FE 24-70mm f/4 ZA OSS Vario-Tessar Carl Zeiss T* lens, but is roughly 20 mm longer, 136 grams heavier and marginally cheaper. Sony also makes a cheaper, lighter FE 28-70mm f/3.5-5.6 OSS lens, but it’s 2/3 stop slower at the wide end and two stops slower at the tele end of the zoom range.
Tamron covers a similar zoom range with its SP AF 28-75mm f/2.8 XR Di LD IF (Model A09) lens but it’s an older design for DSLRs and not optimised for mirrorless cameras. Nor is it weatherproof.
Build and Ergonomics
Unlike Tamron’s ‘SP’ lenses, which have metal barrels, the new 28-75mm f/2.8 lens is made mostly from polycarbonate to keep its overall weight relatively low. Fortunately, build quality is generally good and up to Tamron’s usual standard, which means comfortably above most similarly-priced standard zooms.
A prominent rubber ring forms a dust- and moisture-tight seal around the mounting plate when the lens is fitted to an α7 camera. Both the focus and zoom rings are snug fitting and move smoothly when turned. Missing are premium features like a focus mode switch, focus hold button and zoom lock; but these come with a much higher price tag, more than double the amount asked for this lens.
The zoom ring begins 13 mm behind the front of the lens. It’s 36 mm wide, with a 28 mm wide band of rubberised ribbing providing a slip-free grip and the un-ribbed section behind it carrying stamped markings for the 28mm, 35mm, 50mm and 75mm focal length settings. These line up against a white mark on the fixed section of the outer barrel.
Zooming from 28mm to 75mm extends the inner barrel by 25mm with a firm motion that turns the ring by roughly 90 degrees. The front element of the lens does not rotate, giving scope to use angle-critical filters and other attachments. We also found the lens free of zoom creep, obviating the need for a zoom lock.
Ten millimetres aft of the zoom ring is the focusing ring, which is 14 mm wide and ribbed with finer, shallower moulding. Since manual focus is driven electronically from the camera it lacks a hard infinity stop and can be rotated continuously when the camera is switched off. Manual focusing, therefore, provides less direct feedback than recent Sony lenses.
There are no other external controls on the lens barrel so the focus mode and shake reduction must be set via the camera’s menu. Fortunately, Tamron has designed this lens to be compatible with all the focus mode and focus area settings on α7 cameras, including Direct Manual Focus (DMF), which lets users switch instantly between auto and manual focusing by rotating the focus ring while the shutter button is half-pressed.
Aft of the focus ring the barrel runs straight for approximately 20 mm before sloping inwards for about 8mm to the 13 mm wide section of the barrel that ends with the lens mount. The mount is solid metal with a thin rubber flange surrounding it to exclude moisture and dust. Ten gold-plated contacts inside the mount provide an electronic link between the lens and the camera.
Our Imatest tests showed the review lens to be capable of exceeding expectations for the 12-megapixel sensor in the α7S camera we used for our tests both around the centre of the frame and close to the periphery. We obtained the highest resolution with the 50mm focal length at one third of a stop down from maximum aperture.
Significantly, centre resolution remained high at all focal length settings from 28mm to 75mm with apertures between f/2.8 and f/7.1, where diffraction began to take effect. Edge softening was evident with the shorter focal lengths at apertures up to about f/5. The graph below shows the results of our tests.
Lateral chromatic aberration was entirely within the ‘negligible’ band at all aperture and focal length settings. In the graph of our results below, the red line marks the border between negligible and low CA.
No coloured fringing was observed in uncorrected files with most of our test shots, confirming that chromatic aberration is a minor issue with this lens, particularly when it is used on cameras that provide internal corrections for JPEGs (which includes all α7 models).
Backlit subjects were handled quite well, although the lens was a little flare-prone at times. Slight veiling flare could affect images when a bright light source was just outside the frame and flare artefacts were introduced when the light source was shining directly into the camera.
Since Sony cameras apply corrections to JPEG files when they are produced, we had to examine ARW.RAW files to detect both vignetting and rectilinear distortions. We found vignetting to be common in uncorrected files at f/2.8 at all focal lengths. It’s less severe in the middle of the zoom range than at 28mm and 75mm and quickly reduces as the lens is stopped down. By f/4.5 it’s effectively invisible.
Distortion is also noticeable in uncorrected files. Like most standard zoom lenses it ranges from moderate barrel distortion at 28mm to slight pincushion distortion at 75mm. Both are easy to correct when converting raw files into editable formats and they’re addressed during in-camera JPEG creation.
Close-up shooting performance was aided by the ability of the lens to resolve centre-of-frame details, along with its minimum focus distance of 19 cm at 28mm and 39 cm at 75mm. The former yields a magnification of 1:2.9, while users can obtain 1:4 magnification at 75mm.
We found some curvature of field at the minimum focus distance, particularly with shorter focal lengths with the iris wide open. There were also a few chromatic aberrations in the corners in close-ups, although they would be unlikely to affect normal macro shooting.
Bokeh was generally pleasing, particularly with low-contrast backgrounds, which were softly blurred at f/2.8 at all focal length settings. Bright highlights were rendered as little circles, thanks to the nine-blade iris diaphragm. We found very slight outlining in shots that had bright background elements and traces of onion-ring bokeh in some test shots. Neither could be considered a serious flaw.
Autofocusing was as quick and quiet as Sony’s FE lenses, although not totally silent. Focus accuracy was generally good, even in relatively low light levels. Manual focusing was much as you’d expect from a focus-by-wire lens, which has no mechanical coupling with the camera.
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Picture angle: 75 degrees 23 minutes to 32 degrees 11minutes
Minimum aperture: f/22
Lens construction: 15 elements in 12 groups (including 1 ED, 1 LD, 1 GMA and 2 hybrid aspherical elements)
Lens mounts: Sony E mount (for full-frame format)
Diaphragm Blades: 9 (circular aperture)
Focus drive: RXD (Rapid eXtra-silent stepping Drive) stepping motor
Stabilisation: No (relies on in-camera stabilisation)
Minimum focus: 19 cm at 28mm; 39 cm at 75mm
Maximum magnification: 1:2.9 (Wide) / 1:4 (Tele)
Filter size: 67 mm
Dimensions (Diameter x L): 73 x 117.8 mm
Weight: 550 grams
Standard Accessories: Lens front and end caps, petal-shaped lens hood
Distributor: Blonde Robot; blonde-robot.com.au; (03) 9023 9777
Based on JPEG files from the Sony α7S camera.
Vignetting at 28mm, f/2.8.
Vignetting at 35mm, f/2.8.
Vignetting at 50mm, f/2.8.
Vignetting at 75mm, f/2.8.
Rectilinear distortion at 28mm.
Rectilinear distortion at 35mm.
Rectilinear distortion at 50mm.
Rectilinear distortion at 75mm.
28mm focal length, ISO 100, 1/160 second at f/8.
75mm focal length, ISO 100, 1/125 second at f/8.
Close-up at 28mm; ISO 100, 1/200 second at f/2.8.
Close-up at 75mm; ISO 100, 1/250 second at f/2.8.
Strong backlighting; 28mm focal length, ISO 100, 1/320 second at f/7.1.
Flare artefacts in opposite corners of the frame at 28mm, ISO 100, 1/400 second at f/11.
Slight veiling flare in backlit scene at 28mm, ISO 100, 1/100 second at f/6.3.
Flare at 75mm, ISO 100, 1/200 second at f/11.
Backlit close-up in shade, 75mm focal length; ISO 100, 1/200 second at f/5.6.
Bokeh at f/2.8, 75mm focal length; ISO 100, 1/3200 second.
Shallow depth of field at f/2.8 with 75mm focal length; ISO 200, 1/500 second.
75mm focal length; ISO 200, 1/40 second at f/5.
75mm focal length; ISO 100, 1/60 second at f/7.1.
210mm focal length; ISO 200, 1/800 second at f/8.
28mm focal length; ISO 100, 1/80 second at f/6.3.
32mm focal length; ISO 200, 1/200 second at f/5.6.
75mm focal length; ISO 200, 1/800 second at f/7.1.
Backlit subject; 75mm; ISO 200, 1/100 second at f/8.
190: 75mm focal length; ISO 200, 1/800 second at f/4.
RRP: AU$1299; US$799
- Build: 8.9
- Handling: 8.8
- Image quality: 9.0
- Versatility: 8.9