March 2007 | Margaret Brown
An affordable lens with good performance for photographers seeking a one-lens-for-all-purposes solution.
RRP: $795
Rating (out of 10):
- Build: 9
- Handling: 9
- Image quality: 8.5
- OVERALL: 9
With a zoom ratio of 13.9x, Tamron's new AF18-250mm F/3.5-6.3 Di-II LD Aspherical (IF) Macro lens provides a good single-lens option for DSLR photographers whose cameras have APS-C sized imagers. Weighing less than half a kilogram with the supplied lens hood attached it covers focal lengths equivalent to 27-375mm when fitted on a Nikon, Pentax or Sony DSLR camera or 28.8-400mm on a Canon DSLR.
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With a zoom ratio of 13.9x, Tamron's new AF18-250mm F/3.5-6.3 Di-II LD Aspherical (IF) Macro lens provides a good single-lens option for DSLR photographers whose cameras have APS-C sized imagers. Weighing less than half a kilogram with the supplied lens hood attached it covers focal lengths equivalent to 27-375mm when fitted on a Nikon, Pentax or Sony DSLR camera or 28.8-400mm on a Canon DSLR.
Tamron has a solid track record for developing extended-range zoom lenses and its designers have used several strategies to keep the new lens relatively small and light, most of them based on the successful AF18-200mm F/3.5-6.3 XI Di-II LD Aspherical (IF) Macro lens which is only 0.2mm smaller in diameter and 0.6mm in length. The optical system uses an LD (Low Dispersion) glass element and one AD (Anomalous Dispersion) lens in the first group to minimise on-axis chromatic aberration.
The optical diagram above shows how the Tamron AF18-250mm has been assembled.
Two hybrid aspherical lens elements are included to minimise spherical aberration and astigmatism, while the third lens group has been configured to provide maximum magnification power while maintaining high optical quality. Internal Surface Coatings have been used to minimise flare and ghosting due to reflections from glass surfaces within the lens.
Compact for its range and surprisingly light, the AF18-250mm lens is solidly built and has a wide, rubber-coated zoom ring that is comfortable to use and provides a very smooth and positive zooming action and supported the fast AF system of the Canon EOS 400D, which was used for our tests. A small manual focusing ring near the front of the lens has similar rubber coating and was also very easy to use with the test camera. The supplied 'flower-shaped' lens hood is a bit fiddly to fit but provides excellent glare protection. It reverses onto the lens when not in use. A clip-on lens cap is also provided.
The lens barrel carries position markings for 18, 35, 50, 70, 100, 200 and 250mm focal lengths (in 35mm equivalents), making it easy to pre-set a zoom ratio. A Zoom Lock prevents the lens barrel from extending when the lens is carried face down on a DLSR camera. It's rather small and requires you to use a fingernail to click it on and off, but nonetheless effective. Internal focusing allows the lens to be used with angle-critical filters like polarisers and graduates.
One impressive feature is the ability of this lens to focus down to 45 cm throughout its focal length range. Some impressive close-up shots are possible with the longer focal length settings!
Performance
It's asking a lot of any optical system to cover a zoom range of 13.9 times but the Tamron AF18-250mm lens does surprisingly well. Not unexpectedly, its best performance in our Imatest evaluations was with apertures between f/5.6 and f/16 and focal lengths of 50mm and 70mm. Chromatic aberration was low throughout the zoom range, although we found traces of coloured fringing in some shots at longer focal lengths.
Distortion was also detected at both ends of the zoom range, with slight barrelling at the 18mm position and pincushioning starting at around 50mm. Neither was severe enough to interfere with everyday photography. Edge-to-edge sharpness was very good and we found no evidence of vignetting at wide lens apertures. Flare appeared to be well controlled unless the lens was pointed towards the sun. Bokeh (defocused background/foreground blurring) was attractive - but not outstandingly so.
Subjective assessment of our test shots showed them to be a little lacking in contrast, although the ambient conditions at the time of our test undoubtedly influenced shots. We don't see this as a major problem because it is easy enough to boost contrast when images are edited. Furthermore, it is considered advantageous for raw files to have below-average contrast before they are converted into 16-bit TIFFs.
Overall, the Tamron AF 18-250mm F/3.5-6.3 Di II LD Aspherical (IF) Macro lens represents a good choice for photographers who want a single, all-purpose lens for their DSLR cameras. Although its performance can't match the standard of the best prime lenses - or even zooms with a more limited focal length range - it is an outstanding performer for a long zoom lens. It's also fast enough to be useful for travellers, who will appreciate its compact size, light weight and excellent handling characteristics.
IMATEST GRAPHS
Resolution was very good across the focal length range.
Lateral chromatic aberration was low at all focal length settings and lens apertures.
SAMPLE IMAGES
18mm setting at a standard distance range.
250mm setting from the same position as the shot above.
18mm close-up shot.
250mm close-up from the same position as the shot above.
Coloured fringing example. The enlargement below shows the area outlined by the red rectangle in the shot above.
The Tamron AF18-250mm lens is capable of recording plenty of detail at both normal (above) and telephoto (bleow) focal lengths.
Maximum aperture: f/3.5-6.3 (wide-to-tele)
Minimum aperture: f/22
Lens construction: 16 elements in 13 groups
Lens mount(s): Canon AF, Sony/Maxxum AF-D, Nikon AF-D, Pentax/Samsung AF
Diaphragm Blades: 7
Minimum focus: 45 cm throughout the zoom range
Filter size: 62mm
Dimensions (Diameter x L): 74.4 x 84.3 mm
Weight: 430 grams