Pentax SMC DA 18-250mm f/3.5-6.3 ED AL [IF] - Review / Lab Test Report
Lens Reviews -
Monday, 04 February 2008 05:09
Page 1 of 2
Lens kindly provided by Norbert Warncke!
It is an open secret that the Pentax SMC DA 18-250mm f/3.5-6.3 ED AL [IF] is not a native
design by Pentax but licensed from Tamron. The move isn't even unprecedented - Sony did the
same - and it is actually a good idea. The tests of the Tamron version in Nikon and Canon
mount were promising enough for sure. It is unknown in how far Pentax has added his own spices
to its sibling - it is probably based on Pentax SMC glass elements and it uses, naturally,
a localized finish to match the Pentax way of life.
Typical for DA lenses it covers the APS-C image circle only. The field-of-view is equivalent to
a whopping 28-388mm on full format cameras - that's a 14x zoom ratio and an industry record
at the moment although it'ssurely only an intermediate step to an inevitable 18-300mm incarnation.
Interestingly Pentax managed to keep the price tag fairly close to the "original" Tamron
lens at around 450€/US$ vs 400&euro/US$. The Sony 18-250mm is far more expensive for instance.
In terms of build quality the 18-250mm is a fairly typical Pentax DA lens based
on a combination of plastic and metal parts. The zoom and focus control rings are not the smoothest
around but Ok regarding the target market. The lens uses a duo-cam mechanism (two inner
lens tubes) which extends when zooming towards to long end of the zoom range. At 250mm the lens is
about twice as long as fully retracted (@ 18mm). Surprisingly the duo-cams show only a marginal
tendency of wobbling despite the extreme extension - the question may be whether or how much this
will change over time. The tested sample did not suffer from zoom creeping but Pentax implemented
a transport lock (18mm only) just in case.
The lens has no internal AF motor and relies on a slotted drive screw operated by the
camera. This generates some noise during AF operations and the AF speed is comparatively
slow although reasonably accurate on the K10D. The lens does not feature a Quick-Shift
system like some of the other Pentax zoom lenses.
|Equiv. focal length||27-375 mm (full format equivalent)|
|Equiv. aperture||f/5.3-f/9.5 (full format equivalent, in terms of depth-of-field)|
|Optical construction||16 elements in 13 groups inc. 1x ED and 2x aspherical elements|
|Number of aperture blades||7|
|min. focus distance||0.45 m (max. magnification ratio ~1:3.6)|
|Dimensions||86 x 75 mm|
|Filter size||62 mm (non-rotating)|
|Hood||supplied, petal-shaped, snap-on type|