Above
18mm, f8
As well as being
sharper at the short
end of the zoom
range, the Sigma
has less barrel
distortion than the
other lenses on testLeft
300mm, f8
Sharpness is retained
better at longer zoom
settings than in
competing lenses, but
it still drops off a little
at 300mm. Fringing is
comparatively minimalAbove
Smarter than
the average superzoom
The Sigma feels solid, dependable and
well-engineered. The Canon-mount
option can take advantage of in-camera
corrections for aberrations like
distortion, colour fringing and vignettingsigma’s big zoom range
comes with minimum
compromise in terms of
image quality, and at a very
attractive priceSigma currently offers 18-200mm and 18-
300mm ‘Contemporary’ superzooms in its
Global Vision line-up. This 18-300mm gives
substantially more telephoto reach but is
bigger and heavier. Even so, it’s manageable,
measuring 79-102mm and weighing 585g.
Despite having a more complex build with
an extra (and larger-diameter) element than
the 18-200mm lens, the 18-300mm isn’t
much more expensive in the UK, and both
are about the same price in the USA.
Build quality is good. The barrel sections
and various internal components are
made from Sigma’s TSC (thermally stable
composite) material, which has a quality
feel and remains highly consistent in
size during temperature variations. Themounting plate is metal rather than plastic,
but it doesn’t feature a weather-seal ring.
And like all but the Nikon, the Sigma is
supplied with a petal-shaped hood.
The optical path features four top-grade
FLD (fluorite low dispersion) elements
along with an SLD (special low dispersion)
element. The aim is to deliver optimum
sharpness, contrast and colour fidelity, with
minimal chromatic aberrations. ‘Super
Multi-Layer Coating’ is also applied to
reduce ghosting and flare. The maximum
magnification ratio of 0.33x is about the
same as with the other lenses on test, but
Sigma also offers an optional AML 72-01
‘close-up lens’ (like a screw-in filter), which
boosts macro magnification to 0.5x.Helping to keep the size and weight down,
autofocus is based on an ultrasonic motor
with drive shafts and gearwheels, rather
than a ring-type system. The focus ring
rotates during autofocus and precludes full-
time manual override. On the plus side, the
manual focus ring is small and positioned
right at the front end of the lens, so its
rotation doesn’t really impair handling.
The 3.5-stop optical stabiliser works well,
complete with auto panning detection. The
Sigma edges ahead of all the other lenses
on test for image quality, with greater
sharpness throughout its entire zoom range,
less colour fringing and better control over
distortions. It’s also rather less expensive to
buy, making it standout value for money.x2 © Matthew Richards
group test