A competitively-priced, general-purpose lens with the longest current zoom range and effective image stabilisation.Designed specifically for DSLR cameras with 'APS-C sized' imagers, Tamron's latest ultra-zoom lens, the AF18-270mm Di-II claims to offer the world's largest zoom ratio of any current lens. The 15x zoom covers angles of view that range from the equivalent to a 28mm wide angle to a 419mm ultra telephoto in 35mm format. As such, it represents a genuine 'all-purpose' lens for DSLR users who wish to cover as wide a variety of subjects as possible without having to change lenses. . . [more]
Designed specifically for DSLR cameras with 'APS-C sized' imagers, Tamron's latest ultra-zoom lens, the AF18-270mm Di-II claims to offer the world's largest zoom ratio of any current lens. The 15x zoom covers angles of view that range from the equivalent to a 28mm wide angle to a 419mm ultra telephoto in 35mm format. As such, it represents a genuine 'all-purpose' lens for DSLR users who wish to cover as wide a variety of subjects as possible without having to change lenses.
Naturally, if you want to shoot at high zoom magnifications you need some kind of image stabilisation. Tamron has equipped the new lens with an 'advanced' VC (vibration compensation) mechanism that it claims allows users to shoot with shutter speeds up to four EV steps slower than would otherwise be possible without stabilisation. It also provides more stable viewfinder images to make framing shots easier.
Anti-shake correction relies on three coils arranged in a tri-axial system, which drive a compensator lens electromagnetically via three steel balls that support the optical system. These rolling balls have very low friction and produce fast and silent correction of camera shake, delivering stabilised viewfinder images. This system enables the lens to be mechanically simpler and results in a very small and light DSLR lens for such a long focal length range.
The optical construction of the Tamron AF 18-270mm f/3.5-6.3 Di II VC LD lens showing the location of the special glass elements.
The optical design, shown in the diagram above, consists of 18 elements in 13 groups with two LD (Low Dispersion) glass elements and three aspherical elements to correct common aberrations. Multi-layer coatings have been applied to minimise ghosting and flare. In order to achieve its high zoom ratio, the optical system has no XR (extra dispersion glass) elements. Instead, mechanical construction is simpler and more compact and power distribution has been optimised within the entire optical system, resulting in the smallest, lightest DSLR lens possible for such a long focal length range.
The new lens measures 101mm in length and has a diameter of 79.6mm. It weighs only 550 grams and has a minimum aperture of f/22. Despite being made from lightweight plastic, we consider its build quality to be reasonably good for its price. It has a metal mounting plate and the lens hood and lens cap clip firmly into place and are quick and easy to fit.
The minimum focusing distance is 49 cm over the entire zoom range. Filter diameter is 72mm and seven diaphragm blades close to provide a near-circular iris. A petal-shaped lens hood is supplied as a standard accessory, while a built-in zoom lock mechanism on the top of the zoom ring prevents the barrel from sliding when the lens is being carried on the camera. Two slider switches near the camera body end of the lens barrel enable the autofocus and vibration correction to be switched on and off.
The focusing ring, which is approximately 20mm wide, lies towards the front, while the zoom ring, which is approximately 45mm wide is closer to the camera body. Both rings have ridged rubber coatings to provide a secure grip. The ridges on the focusing ring are wider than those on the zoom ring but the ring itself is narrower.
The trailing edge of the focusing ring carries engraved focus distance markings in metres and feet, with the closest mark at 0.49 metres. The trailing edge of the zoom ring is engraved with the following focal length settings: 18mm, 35mm, 50mm, 70mm, 100mm, 200mm and 270mm. The maximum and minimum apertures change with focal length as shown in the table below.
Focal length setting
The review lens felt nicely balanced on the Canon EOD 40D body we used for our tests. The zoom movement was positive, with slightly increased resistance between the 35mm and 100mm focal length settings. Moving through the zoom range requires roughly a third of a turn and causes the front of the lens to extend by approximately 90 mm. The front element does not rotate during zooming, allowing use of angle-critical filters, such as polarisers and graduates.
The focusing ring moved freely through approximately one sixth of a turn in manual focus mode but could not be used when the slider was set to the AF position. We found no tendency for the lens to extend when the camera was carried with the lens pointing downward, even when the zoom lock was not engaged. Nor did we observe any unwanted changes in focal length as focus was adjusted.
The review lens's autofocusing system was reasonably fast and accurate in bright conditions but we noticed a tendency to hunt in dim lighting, particularly at longer focal length settings. With close subjects the AF system occasionally failed to lock onto the subject, instead finding focus on the background. We had to switch to manual focusing in such situations. Fortunately autofocusing was almost silent, an asset for wildlife photographers.
The VC image stabilisation system has only two modes: continuous and off. You can't set stabilisation to operate in only one direction as you can with some other lenses so to get the best results with panning shots you usually have to switch the stabiliser off. However, one advantage of using VC is that the viewfinder image is also stabilised, which makes it much easier to compose shots with longer focal length settings.
Imatest showed the review lens to be a competent performer for its focal length range and price tag. We obtained the best resolution results at the 18mm focal length with aperture settings between f/8 and f/13 but relatively low resolution at the widest aperture settings. Overall resolution performance was better on average with focal lengths between 35mm and 150mm at apertures between f/4.0 and f/11.
Diffraction began to affect image quality from about f/13 on and by f/22 test shots were noticeably softened. We would not recommend using this lens at apertures smaller than f/18. The graph below shows the results of our Imatest tests.
Imatest showed very little evidence of edge softening. In fact, the results of our tests showed the review lens had a surprisingly flat field at all aperture and focal length settings. This was confirmed by subjective assessments of test shots, which were subjected to very close scrutiny for the longer focal lengths as Photo Review is unable to run Imatest tests for focal lengths beyond 150mm because there is insufficient distance leeway in our testing set-up.
For a lens with such an extended zoom range, lateral chromatic aberration was remarkably low. The graph below shows the results of our Imatest tests. Note: the red line marks the boundary between negligible and low CA values.
Autofocusing was reasonably fast and accurate in most lighting conditions, although some slowing was noticed, along with a tendency to hunt, in low light levels. We found the VC system could provide up to six f-stops of shutter speed advantage at the full tele zoom - as long as we were prepared to discard roughly two thirds of the test shots we took. Under these conditions we were able to use the 270mm focal length setting at shutter speeds as slow as 1/6 second. Two examples are shown below.
Indoor shot, hand held at 270 mm focal length, 1/6 second at f/6.3.
Outdoor shot, hand held at 270 mm focal length, 1/8 second at f/6.3 (note the slight loss of sharpness).
On average, however, we feel most normal shooters should consider the VC system as offering an average of 3.5 f-stops of advantage for most shooting conditions. This is a more realistic expectation if you expect almost all of the shots to be reasonably sharp.
Flare and ghosting were generally very low, thanks to the internal surface coatings in the lens, and we found no fault with overall colour or tonal reproduction, even with relatively strong backlighting. We also found no apparent vignetting at any focal length setting. Barrel distortion was obvious at the 18mm focal length, reducing at around 35mm then segueing into pincushion distortion at around the 50mm focal length mark.
Close-up performance was unspectacular and the focusing limit of almost half a metre made the lens a clumsy choice for macro work. Bokeh tended to be slightly busy when the background was within about a metre of the subject, even at longer focal lengths with the widest available aperture settings. Stopping down even a couple of f-stops tended to emphasise the busyness but subjects with more distant backgrounds showed more attractive blurring.
Overall, Tamron's AF18-270mm f/3.5-6.3 Di II lens is more worthy of praise for what it can do than for its faults. As a lightweight, all-in-one solution for everyday picture-taking it's a good performer on the whole and would make a fine travelling companion, especially for photographers who don't make large prints.
The new lens is available in both Canon and Nikon mounts - but not Sony or Pentax (as yet). Nikon users will be happy to learn that the Nikon version includes a built-in AF drive motor and electronic contacts that can adjust the aperture diaphragm. This enables it to be used on camera bodies like the D40 and D60 which don't require lenses with aperture rings.
Some interesting simulations of the zoom range and stabilisation system can be found at http://www.tamron.com/B003special/sim.html. It's worth checking them out if you are interested in this lens.
Buy this lens if:
- You don't like changing lenses - or have a camera body without built-in dust removal - and want a single, all-purpose lens that covers most shooting situations.
- You require an affordable 'walk around' lens for travelling or everyday photography.
- You want a long zoom lens with effective image stabilisation for both the viewfinder image and the capture system.
Don't buy this lens if:
- You have a camera with a 'full frame' (36 x 24mm) image sensor.
- You need a fast lens across the focal length range for shooting action in dim lighting.
- You plan to print your images to A3 size or larger.
- You need a distortion-free lens.
- You want macro versatility and performance.
18mm focal length, 1/100 second at f/16.
270mm focal length, 1/100 second at f/16.
270mm focal length, 1/100 second at f/18.
Crops from the centre (top) and edge (bottom) of the above image show softening due to diffraction. (Note the coloured fringing along the edge of the sail in the right hand crop.)
168mm focal length, 1/100 second at f/18.
270mm focal length, I/250 second at f/6.3.
65mm focal length, 1/350 second at f/11.
270mm focal length, 1/125 second at f/6.3.
270mm focal length, 1/180 second at f/8.
154mm focal length, ISO 640, 1/30 second at f/5.6. (Nicer Bokeh here because subject is closer to the camera.)
Strong backlighting: 18mm focal length, ISO 100 1/125 second at f/16.
270mm focal length, 1/350 second at f/6.7.
Picture angle: 5 degrees 55 minutes to 75 degrees 33 minutes
Maximum aperture: f/3.5 to f/6.3
Minimum aperture: f/22 to f/40
Lens construction: 18 elements in 13 groups
Lens mount: Canon and Nikon
Diaphragm Blades: 7
Minimum focus: 0.49 metres
Maximum magnification: 1:3.5 (at f = 270mm, MFD : 0.49m)
Filter size: 72 mm
Dimensions (Diameter x L): 79.6 x 101.0 mm
Weight: 550 grams
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