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)

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-




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