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)
Thursday, 27 December 2007 03:16
Page 1 of 3
Lens kindly provided by Tamron Europe!
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.
|Equiv. focal length||29-400 mm (full format equivalent)|
|Equiv. aperture||f/5.6-f/10 (full format equivalent, in terms of depth-of-field)|
|Optical construction||16 elements in 13 groups inc. 1x AD, 2x LD and 2x hybrid aspherical elements|
|Number of aperture blades||7|
|min. focus distance||0.45 m (max. magnification ratio ~1:3.5)|
|Dimensions||84 x 83 mm|
|Filter size||62 mm (non-rotating)|
|Hood||supplied, petal-shaped, snap-on type|