Sony DT 18-135mm f/3.5-5.6 SAM Lens
Sony’s new DT 18-135mm f/3.5-5.6 SAM lens has been developed to cover the focal lengths that are most frequently used by everyday photographers. This lens is designed for cameras with APS-C sized sensors and provides field-of-view coverage equivalent to 27-202.5mm in 35mm format. A good choice for photographers who want a single lens to go with their camera body, it produces sharp images with low levels of common aberrations.
The DT 18-135mm f/3.5-5.6 SAM lens, pictured without caps and supplied lens hood. (Source: Sony.)
Its optical design consists of 14 elements in 11 groups and includes a single ED (Extra-low Dispersion) glass lens element as well as a pair of aspherical lens elements to minimise common aberrations and subdue flare. The AF motor is Sony’s proprietary Smooth Autofocus Motor (SAM), an internal motor that doesn’t rely on the old screw-driven AF system operated by the camera.
SAM motors provide reasonably fast autofocusing, combined with a fairly low noise level, making the SAL-18135 quieter than other entry-level model lenses in Sony’s line-up. This lens supports Direct Manual Focus (DMF), which allows users to switch between AF and MF without removing their eyes from the viewfinder.
The lens is supplied with front and end caps plus a deep, petal-shaped lens hood with a bayonet attachment that reverses onto the lens for storage. Multi-lingual instructions sheets are also provided, although they’re not particularly informative.
Build and Ergonomics
Build quality is a cut above Sony’s normal kit lenses, thanks to a metal mounting plate and higher quality fit and finish. Although the lens barrel is largely made from polycarbonate plastic it is solid and has a ‘quality’ feel. Weighing only 398 grams and just 73 mm long, it is compact enough to be an excellent ‘travelling’ lens when partnered with one of Sony’s lighter SLT-A series cameras.
The zoom ring is 33 mm wide and starts about 10 mm back from the front of the lens. It feels quite tight but moves smoothly and positively as you span the focal length range. It takes roughly a quarter of a turn to zoom from 18mm to 135mm, which extends the inner barrel by approximately 58 mm. The inner barrel consists of two pieces, which are closely integrated but move different distances.
The zoom ring carries a 25 mm wide rubber grip band with narrow parallel ridges. Focal length distanced for 18mm, 24mm, 35mm, 50mm, 70mm, 100mm and 135mm are stamped around the trailing edge of this ring for lining up against a white line on the fixed section of the outer lens barrel just behind the ring.
A zoom lock is provided to the right of the 18mm position to prevent the lens from extending when you don’t want it to. (We never needed to use it.)
The focusing ring is a little slacker and it’s located roughly seven millimetres behind the zoom ring. Approximately 12 mm wide, it is covered with a ridged, rubber grip.
This ring can be rotated through 360 degrees in both AF and MF modes. There’s a slight resistance at one point but without a distance scale, we wouldn’t determine precisely where.
A slider for switching between AF and MF is located on the left hand side of the lens barrel behind the focusing ring. The front element does not rotate during focusing or zooming, allowing use of angle-critical attachments like polarisers.
Our shooting tests were carried out with the Sony SLT-A57 camera, which is reviewed separately. The review lens was a comfortable fit on this camera body and its relatively small size created a good balance for shooting both stills and movies.
In our Imatest tests, JPEG files taken with the lens on the A57 body came close to meeting expectations for the sensor resolution and edge and corner softening were relatively low across the focal length and aperture ranges supported. The graph below shows the results of our tests.
The highest resolution figures were recorded between one and three f-stops down from maximum aperture. Diffraction began to affect resolution from about f/8, with a steady decline down to f/22.
Lateral chromatic aberration was mostly negligible, wandering into the ‘low’ band at aperture settings of f/5.6 and smaller for the 100mm and 135mm focal lengths. In the graph of our Imatest tests below, the red line marks the border between ‘negligible’ and ‘low’ CA, while the green line marks the beginning of the ‘moderate’ CA band.
You can set the A57 to correct this aberration so it’s largely irrelevant for owners of the new camera. We found no significant signs of coloured fringing in test shots when correction was switched off.
Correction of rectilinear distortions is also available in-camera. With this correction switched off, the lens shows noticeable barrel distortion between 18mm and 35mm. Thereafter, the field of view appeared to be relatively flat.
Vignetting was slight enough to be negligible at f/3.5 with the 18mm focal length and reduced as focal length was increased. It was not evident at the longest focal lengths, even with wide aperture settings.
Backlighting was handled extremely well and it was difficult to force the lens to flare when the lens hood was in place. Close-ups were also quite successful when the 135mm focal length was used at the close-focusing limit of 45 cm. Bokeh was smooth and attractive.
Buy this lens if:
– You want a compact and lightweight general-purpose zoom lens for everyday and travel photography and shooting movies with a Sony DSLR.
– You require superior performance and good flatness of field.
– You’d like a lens that requires no readjustment when you fit polarisers and graduated filters.
Don’t buy this lens if:
– You need true macro capabilities.
– You don’t use a Sony SLT-A series camera.
Picture angle: 76 to 12 degrees
Minimum aperture: f/22
Lens construction: 14 elements in 11 groups, including 2 aspheric and 1 ED glass elements
Lens mount: Sony A-Mount (Minolta AF)
Diaphragm Blades: 7 (circular aperture)
Focus drive: Internal focusing via Smooth Autofocus Motor (SAM) with Direct Manual Focus (DMF)
Stabilisation: No (sensor-shift in camera body)
Minimum focus: 45 cm
Maximum magnification: 0.25x
Filter size: 62 mm
Dimensions (Diameter x L): 85.5 x 73 mm
Weight: 398 grams
(based on JPEG files from the Sony SLT-A57)
Vignetting at 18mm, f/3.5.
Vignetting at 135mm, f/5.6.
Distortion at 18mm.
Distortion at 135mm.
18mm focal length, 1/80 second at f/10, ISO 100.
135mm focal length, 1/15 second at f/8, ISO 100.
Controlled flare; 30mm focal length, 1/640 second at f/13, ISO 100.
Strong backlighting; 35mm focal length, 1/2000 second at f/11, ISO 200.
Close-up in Macro mode; 135mm focal length, 1/320 second at f/6.3, ISO 100.
135mm focal length, 1/250 second at f/11, ISO 250.
AF Tracking with continuous shooting – beginning of burst; 90mm focal length, 1/1000 second at f/5.6, ISO 250.
AF Tracking with continuous shooting – end of 20-shot burst; 90mm focal length, 1/1000 second at f/5.6, ISO 320.
In-camera chromatic aberration switched off; 18mm focal length, 1/125 second at f/5.6, ISO 100.
Crop from the above image, enlarged to 100% to show little evidence of coloured fringing.
Additional image samples can be found with the review of the Sony SLT-A57 camera.
RRP: AUD $649; US$500
- Build: 8.5
- Handling: 8.5
- Image quality: 8.5
- Versatility: 9.0