N-Photo

STANDARD DX ZOOMS

A CONSTANT-APERTURE BARGAIN A SMART NEW ‘CONTEMPORARY’ LENS

Sigma 17-50mm f/2.8

EX DC OS HSM £ 3110 , $ 4220

Sigma 17-70mm f/2.8-4 DC

Macro OS HSM | C £ 3330 , $ 4000

The ‘EX’ designation of this lens
predates Sigma’s Art, Sport and
&RQWHPSRUDU\FODVVLÀFDWLRQV
(YHQVRLWVLJ QLÀHVLW ·VRQHRI
Sigma’s ‘professional-grade’
lenses and, as such, it has a high
standard of build quality and
ÀQLVKDORQJZ LW KDFRQVWDQW
f/2.8 aperture. That’s all pretty
remarkable, considering the
modest asking price.
Look closer, though, and
there are signs that it’s not
what you might call a fully
professional lens. The HSM
(HyperSonic Motor) autofocus
system is motor-driven, rather
t ha n r i ng-t y pe, a s i n Ni kon’s
18-55mm kit lens. As such,
the focus ring rotates during
autofocus. There’s better news
when it comes to the optical
path, which includes two
top-spec FLD (Fluorite-grade
Low Dispersion) elements.

Performance

Autofocus is pretty quiet and
fast but, while centre sharpness
is excellent even at wide
apertures, corner sharpness is
relatively poor. Colour fringing
can also be noticeable in the
corners, but vignetting and
distortions are restrained.

In the UK, this lower-spec,

variable-aperture lens is pricier

than Sigma’s own 17-50mm

f/2.8. However, it’s a newer

design, updating Sigma’s

previous 17-70mm and joining

the C-class (Contemporary)

fold. As such, it’s smartly

W XU QHGRXWDQGQLFHO\ÀQLVKHG

and built for compactness, light

weight and easy handling. Even

so, there’s room inside for two

FLD (Fluorite-grade Low

Dispersion) elements, matching

Sigma’s bulkier f/2.8 lens.

One thing Sigma didn’t

upgrade was its autofocus

system, which remains an

ultrasonic motor design. As

such, it suffers from the same

rotating focus ring as the older

lens, with the same lack of

full-time manual override.

Performance

Autofocus is fairly fast and very

quiet, and the optical stabiliser

is good for close to four stops.

Centre sharpness is passable

at the 17mm focal length, but

drops off a bit at mid to long

]RRPVHWWLQJV7KHÁLSVLGH

is that this lens retains corner

sharpness much better than its

17-50m m sibling.

Great at the centre, but you need to stop

down to f/5.6 before corners come good.

It’s not too special, but at least sharpness

i s f a i r l y eve n a c ro s s th e w h o l e f r a m e.

f/4-5 f/5.6 f/8 f/11 f/16 f/22 f/32

0

500

1000

1500

2000

2500

f/2.8-3.5

17mm 28mm 35mm 50mm

f/4-5 f/5.6 f/8 f/11 f/16 f/22 f/32

0

500

1000

1500

2000

2500

f/2.8-3.5

17mm 35mm 50mm 70mm

Centre sharpness (Higher is better) Centre sharpness (Higher is better)

Short 2.9 Mid 2.09 Long 2.51

Performance for fringing is good rather

than great. Similar to the Nikon 18-105mm.

Edge fringing (f/8) (Lower is better)

Short 2.48 Mid 1.32 Long 1.16

Colour fringing is a little better controlled

than in the Sigma 17-50mm.

Edge fringing (f/8) (Lower is better)

Features

Build/Handling

Performance

value for money

OVERALL

It’s good value for a constant-aperture

f/2.8 lens, with pleasing performance.

Verdict

Features

Build/Handling

Performance

value for money

OVERALL

It’s a neat and compact lens, but centre

and corner sharpness could be better.

Verdict

There’s not too much distortion, in

ke e p i n g w i th th e m o d e s t zo o m r a n ge.

Distortions are fairly low, considering

the zoom range is longer than average.

Distortion (Nearer 0 is better) Distortion (Nearer 0 is better)

-3 -2 -1 0 123

SHORT -2.54

MID 0.58

LONG 1.05

-3 -2 -1 0 123

SHORT -2.71

LONG 1.36

MID 0.69

http://www.digitalcameraworld.com March 2016 131