Tamron AF 18-250mm f/3.5-6.3 Di II LD Aspherical [IF] macro (Canon) - Review / Test Report
Lens Reviews - Canon EOS (APS-C)

Review by Klaus Schroiff, published June 2007

Lens kindly provided by Tamron Europe!

Introduction

Back in the 1992 Tamron started the extreme or "super" zoom era with the release of the the AF 28-200mm F/3.8-5.6 Aspherical, a 7.1x zoom ratio lens. At the time it was quite a sensation whereas today such lenses have found their way into the heart of the mainstream. Tamron released various new incarnations over time including the 28-300mm (10.7x) and the first dedicated APS-C super-zoom - the 18-200mm XR (11.1x) - and this year they pushed it even further with the new Tamron AF 18-250mm f/3.5-6.3 Di II LD Aspherical [IF] macro breaking the existing zoom ratio record again (13.9x) - the zoom range translates a field-of-view equivalent to a 28-388mm (full format). Normally you would expect such a beast to be fairly massive but Tamron is also renowned for lens miniaturization and the 18-250mm isn't any bigger than a typical mid-range zoom. One of the reasons for this is surely the very slow max. aperture of f/6.3 @ 250mm. This is a bit of a borderline approach because most AF system are only specified till f/5.6 (officially) and you need quite a bit of light (or high ISO) to use this lens hand-held.

In terms of build quality the Tamron is a fairly typical consumer grade zoom lens. Most of the outer construction is made of plastic except for the metal mount (which is an upgrade compared to the old 18-200mm XR). The broad rubberized zoom ring has a fairly high friction and it wobbles a little whereas the small focus ring operates reasonably smooth although somewhat "lifeless". The lens uses a duo-cam zoom mechanism (two inner lens tubes) to extend towards to long end of the zoom range. At 250mm the lens is about twice as long as full retracted (@ 18mm). Surprisingly the duo-cams showed no tendency to wobble despite the extreme extension. The tested sample did not suffer from zoom creeping (which may develop over time) but Tamron implemented a transport lock (18mm only) just in case.

The Tamron uses a conventional AF micro-motor. Thanks to a very short focus path (~30 degrees) the AF speed is relatively fast - on the EOS 350D it takes about a second to AF from infinity to the min. focus distance. Interestingly most of the focus range is used for conventional distances - 1m to infinity covers about 3/4 of the total focus path (starting at 0.45m). This is quite unusual and probably the reason why some users complained a little about the AF speed. The AF accuracy was fine from about 35mm to 250mm but a little unsure at the very wide end (the 350D is not overly reliable here anyway). Manual focusing is difficult because a fractional turn of the focus ring results already in a very pronounced focus shift. However, the priority on AF rather than MF is probably a valid approach regarding the target market.

Specifications
Equiv. focal length29-400 mm (full format equivalent)
Equiv. aperturef/5.6-f/10 (full format equivalent, in terms of depth-of-field)
Optical construction16 elements in 13 groups inc. 1x AD, 2x LD and 2x hybrid aspherical elements
Number of aperture blades7
min. focus distance0.45 m (max. magnification ratio ~1:3.5)
Dimensions84 x 83 mm
Weight430 g
Filter size62 mm (non-rotating)
Hoodsupplied, petal-shaped, snap-on type
Other features-