February 2008 | Margaret Brown
A high-quality, general purpose lens for Sony's Alpha digital cameras.
RRP: $1,249
Rating (out of 10):
- Build: 8.5
- Handling: 8.5
- Image quality: 9
- Versatility: 8.5
- OVERALL: 8.8
Designed to suit the 23.6 x 15.8mm image sensors on Sony's Alpha DSLR cameras, the new Carl Zeiss Vario-Sonnar T* DT 16-80mm F3.5-4.5 ZA lens covers a focal length range equivalent to 24-120mm in 35mm format. Although described as 'the first professional-grade 5x zoom lens specifically designed for APS format DSLRs' it's probably better seen as a 'pro-sumer' lens. It's an excellent general-purpose lens for the A700 and A350 models, whose high resolutions can capitalise on its performance.
. . [more]
Designed to suit the 23.6 x 15.8mm image sensors on Sony's Alpha DSLR cameras, the new Carl Zeiss Vario-Sonnar T* DT 16-80mm F3.5-4.5 ZA lens covers a focal length range equivalent to 24-120mm in 35mm format. Although described as 'the first professional-grade 5x zoom lens specifically designed for APS format DSLRs' it's probably better seen as a 'pro-sumer' lens. It's an excellent general-purpose lens for the A700 and A350 models, whose high resolutions can capitalise on its performance.
Combining Carl Zeiss optical design with Sony construction, the 16-80mm lens is made in Japan and carries both Zeiss and Sony branding, indicating the collaboration between the two companies. It is constructed from 14 elements in 10 groups and includes two glass moulded aspherical lenses to minimise spherical aberrations. Carl ZeissT* coatings subdue internal reflections and prevent flare and ghosting.
The above diagram shows the construction of the lens. The aspherical elements are shown in purple.
Build quality is good - but not outstanding. The lens barrel is made from polycarbonate plastic (for lightness) and the zoom and focusing rings have ridged rubber coatings that provide a decent grip - although we found they tend to trap grit. Both rings are relatively wide, with the zoom ring slightly wider than the focusing ring.
The focusing ring is towards the front, while the zoom ring is closer to the camera body. Between them is a distance scale with feet and metre markings at 0.36, 0.6, 1 and 3 metres plus infinity for manual focusing. No depth of field or infrared indicators are provided. The zoom ring has engraved marks for 16, 24, 35, 50 and 80mm focal lengths, which are lined up against an indicator mark on the lens barrel. Zooming to the 80mm position almost doubles its length of the lens barrel.
The focusing ring can only be adjusted when the camera is set for manual focusing by moving the slider switch near the lens release button on the front panel. Autofocusing is, therefore, driven by the camera. In AF mode, an auto clutch mechanism decouples the focus ring from the AF gear mechanism, preventing it from rotating during focusing.
Focusing movements are internal so the front element does not rotate, allowing angle-critical attachments like polarisers and graduates to use fitted. Distance encoding on the lens provides ADI flash metering support.
The lens is supplied with a petal-shaped lens hood, which reverses onto the lens for storage. Fitting it can be tricky as you have to line up an orange dot on the hood with one on the lens and snap it into place with a 90-degree rotation. Once in place, it is very secure and provides good protection for the front element. Its inner surface has a matte coating to suppress reflections.
End caps and a soft case are supplied with each lens. The lens cap, which carries both the Zeiss logo and a discrete Alpha symbol, fits with standard spring clips that are large enough to grip easily when the lens hood is in position.
Handling
The review lens fitted snugly onto the A350 body (which we used for our tests) with a very positive click-in fit. It was a comfortable, well-balanced match for the A350 and would be equally at home on the larger A700 or smaller A200 models.
Once in place, the zoom moved smoothly - although not inaudibly. Moving from the 16mm to the 80mm position required roughly a quarter of a turn. The zooming movement was relatively smooth but we had the impression of plastic sliding on plastic as we zoomed in and out. This did not affect zoom performance - or accuracy - but was slightly disconcerting for a lens with such a pedigree. No zoom lock is provided and it seems unnecessary as the lens stayed put when the camera was carried facing downwards.
The focusing ring only moves through about a sixth of a turn, which can make focusing accurately difficult with close subjects. However, it can be used with the live view setting and you can check focus on the LCD monitor. The movement of the focusing ring had the same plastic-on-plastic feel as the zoom ring, but was slightly less smooth.
Screw-on filters are fitted normally to the front lens element. Internal focusing allows the lens to be used with angle-critical filters like polarisers and graduates. You can also fit external filter holders, such as those in the Cokin range.
Performance
Autofocusing was generally fast and accurate under most shooting conditions and we found few instances of hunting in dim lighting. In our Imatest evaluations, the test lens produced resolution levels that ranged from very good to excellent, with a 'sweet spot' between f/4.0 and f/11. The graph below plots the results of our tests for different focal lengths and lens apertures with unbroken lines representing readings from near the centre of the image field and the dotted lines representing readings close to the edge.
Lateral chromatic aberration varied with the lens focal length setting but was mainly in the 'low' and 'insignificant' categories. The graph below shows the average of our results for each focal length setting.
The red line marks the border between the 'insignificant' and 'low' levels of lateral chromatic aberration.
Vignetting (edge darkening) was barely visible at all apertures and focal length settings. Corner softening was only just apparent at 16mm. Rectilinear distortion was visible at the 16mm setting but negligible by 24mm. We observed very slight pincushion distortion at the 50mm and 80mm settings. None of these aberrations would be enough to affect general photography.
Although the 16-80mm lens is relatively slow, bokeh (out-of-focus blur) was relatively smooth and quite attractive, as shown in the photograph below. However, the relatively small size of the sensor and smallish maximum aperture at the 80mm setting made it difficult to obtain truly out-of-focus backgrounds with most subjects.
We found some evidence of flare in shots taken with the lens pointing towards the sun, mostly in the form of a series of bright blotches across the image (as shown below). Fortunately, contrast appeared to be maintained for most contre-jour shots and there was no evidence of veiling flare.
Picture angle: 83°-20° (on Sony DSLR cameras)
Minimum aperture: f/22-f/29
Lens construction: 14 elements in 10 groups with 2 aspherical elements
Lens mount: Sony Alpha mount
Diaphragm Blades: 7
Minimum focus: 35 cm
Filter size: 62mm
Dimensions (Diameter x L): 72 x 83 mm
Weight: 445 grams