Camera Accessories

Usable with both DSLR cameras and 35mm AF-SLR film cameras, Tamron's new AF28-300mm F/3.5-6.3 XR Di lens is designed for use with DSLR cameras that lack sensor-shift image stabilisation (Canon and Nikon). It provides an angle of view equivalent to approximately 43-465mm on cameras with 'APS-C' sized imagers. Relatively compact and lightweight for its class, it will attract travellers and photographers who want a single, extended-range lens with a wide coverage.

The optical system includes elements made from special optical glass materials including XR (high refraction index) glass elements, GM (glass-moulded aspherical lens) elements, hybrid aspherical elements, LD (low dispersion) glass elements to compensate for on-axis and lateral chromatic aberrations and AD (anomalous dispersion) glass element. Together they deliver high contrast, high resolution performance and flatness of the image field.


The diagram above shows how the lens elements are arranged. (Source: Tamron.)

A proprietary Vibration Compensation (VC) mechanism is built into the lens to counter camera shake. It uses three pairs of driving coils and steel balls around the compensator group of the lens' optical system. The compensator lenses are supported with rolling friction of the balls to maximise responsiveness. Gyro sensors detect hand-shake in both pitch and yaw directions and a 32-bit RISC CPU drives the compensatory mechanisms.  The diagram below shows how the various components are arranged.


The diagram above shows the construction of the VC mechanism. (Source: Tamron.)

This design ensures a stable viewfinder image in a very compact lens. Vibration Compensation can be switched off via a slider on the lens barrel, which is located just below the AF/MF slider switch.

A minimum focusing distance of 49 cm is maintained throughout the zoom range, providing a maximum magnification ratio of 1:3 at the 300mm telephoto position. Internal surface coatings minimise the effects of internal reflections, flare and ghosting. Internal focusing allows the use of angle-critical filters, such as polarisers and graduates. A zoom lock is provided to prevent unwanted barrel extension when carrying the lens/camera combination vertically.

The lens barrel is solidly designed with a broad zoom ring and narrow focusing ring, the latter located towards the front. Both rings have textured rubber coatings, which provide an excellent grip. Just in front of the focusing ring is an etched distance scale in feet and metres, with markings at 0.49, 1, 3.2, 7 and 30 metres plus infinity. No depth of field or infrared indicators are provided.

Rear of the zoom ring are focal length markings for 28mm, 35mm, 50mm, 70mm, 100mm, 135mm, 200mm and 300mm positions. A flower-shaped lens hood is included as a standard accessory. The hood reverses over the lens when it is not in use and locks into place with a bayonet mounting. A clip-on lens cap is supplied.

Handling
In use, the AF28-300mm lens felt equally comfortable on the Canon EOS 40D and EOS-1Ds Mark III cameras we used for our tests. The focusing ring can only be moved when the AF/MF switch is set to MF. It's not quite as tight as the zoom and moved more readily, covering the entire focusing distance in roughly one sixth of a turn.

The zoom ring moved smoothly and showed no tendency to 'creep'. Moving from the 28mm to the 300mm setting involved just over a third of a turn and making precise intermediate adjustments was relatively easy. Both the AF/MF and VC ON/OFF switches clicked into place positively and swapping between settings was fast and easy. Close focusing capabilities are impressive for such a long zoom, with a 1:3 reproduction ratio down to 49 cm throughout the focal length range.  

Performance
Considering the range of the zoom, the AF28-300mm F/3.5-6.3 XR Di's overall performance was surprisingly good. Test shots were not quite as 'punchy' as you would expect from a shorter zoom (or prime lens), but they would be considered acceptable by the majority of non-professional photographers. Lateral chromatic aberration was generally low and we found no coloured fringing in any of our test shots.

We obtained the best results in our Imatest tests with the 28mm setting. Performance tailed off at longer focal lengths, particularly when the lens was tested on the EOS-1Ds Mark III. At all focal lengths, centre resolution was higher than edge resolution but the differences were greater with in test shots from the EOS 40D (which has a smaller sensor) than the 'full-frame' EOS-1Ds Mark III. The graphs below show the test results at three focal length settings across the zoom range of the lens for each camera used in the tests.

Tamron makes no claims concerning the degree of exposure advantage the VC image stabilisation system allows. Going by our experiences, we would say it provides between three and four f-stops at the 28mm setting but roughly two stops at 300mm. When we tried hand-holding a shot at 1/30 second at 300m the result was slight (though detectable) blurring.

Overall sharpness was somewhat less than you can achieve with prime lenses - or even shorter zooms. This is to be expected, given the design compromises that are made to create such a long zoom lens. Bokeh (out-of-focus blurring) was generally attractive. Flare and ghosting were negligible.

We observed slight barrel distortion in wide-angle shots and minor pincushioning between about 100mm and 250mm. However, neither would have a noticeable effect on everyday photography.  

Conclusion
Given its extended focal length range, the Tamron AF28-300mm F/3.5-6.3 XR Di VC LD lens represents excellent value for money. It would be a good choice for photographers who want a DSLR body with just one extended-zoom lens. Its focal length range covers angles of view that will suit many different types of photographers. Its relatively light weight, compact size and robust construction make it particularly suitable for travellers.

SAMPLE IMAGES

From EOS 40D

300mm, 1/664 second at f/9.9

84mm, 1/300 second at f/11 

184mm, 1/500 second at f/8

300mm, 1/400 second at f/7.1

28mm, 1/250 second at f/8

300mm, 1/300 second at f/6.3

135mm, 1/200 second at f/7

300mm, 1/80 second at f/5.6

From EOS-1Ds Mark III

300mm, 1/790 second at f/8

300mm, 1/400 second at f/8

300mm, 1/500 second at f/9.1

300mm, 1/500 second at f/7.1

300mm, 1/125 second at f/6.4

28mm, 1/125 second at f/7

Focal length range: 28-300mm
Picture angle: 8 degrees 15′ to 75 degrees 23′
Minimum aperture: f/22-f/40
Lens construction: 18 elements in 13 groups
Lens mount(s): Canon AF, Nikon AF-D
Diaphragm Blades: 9
Minimum focus: 0.49 m
Filter size:  67mm
Dimensions (Diameter x L): 78.1 x 101.5 mm (Canon mount); 78.0 x 99.0 mm (Nikon mount)
Weight: 558 grams