OBIECTIV SIGMA

OBIECTIV SIGMA 55-200MM 1:4-5.6 DC,PERFECTA STARE.

As a popular focal length range for purchase as a second lens on cropped sensors, and often offered in twin lens kits, this lens, starts at the point where most standard kit lenses finish and goes out to a good medium telephoto length. We take a look at how this offering from Sigma, designed for cropped sensors only, performs.

• Focal Length 55-200mm
• Construction 12/9 elements/groups
• Max aperture f/4-5.6
• Angle of view Sensor dependent
• Closest focus 1.1m
• Filter thread 55mm
• Dimensions 71.5x87.1mm
• Weight 0.31kg
• Hood yes (supplied)
• Mounts available Sigma, Canon, Nikon, Pentax, Minolta, Four-thirds

Build and handling
This DC lens from Sigma is the only independent available in the four thirds mount that is attracting more interest of late. It is also the only one in its class with a proper, full sized manual focus ring. That in itself is to be commended, enabling newcomers to the hobby to learn the advantages of being able to manual focus.
Build quality, for the class, is one of the better ones with a good looking matt finish to the plastic body being capped off with a metal mount. There is a slide switch in the normal place for the AF/MF changeover, in front of which is a 20mm zoom ring with a rubber ribbed grip and marked at the focal lengths of 55, 70, 105, 135 and 200mm.

Next, the barrel steps down a tad to the manual focus ring, complete with a distance scale marked in metres and feet. This furnishes a 16mm raised, rubberised grip area. The front element extends as a single tube, some 30mm when fully zoomed out plus another 10mm at the closest focus of 1.1m, giving a reproduction ratio of 1:4.5 at best. The only disadvantage of this design is that the front element does rotate during focussing, a hindrance when using polarising filters.

Autofocus is a little noisy and not as fast as lenses with HSM motors but it did cope with most everyday situations and locked on with good accuracy. The supplied cup shaped hood fitted, bayonet style with a positive click.

Optical quality
As with most budget zoom lenses, this model from Sigma benefits from being stopped down and is a better performer at the shortest end of the focal length range. As the focal length increases, the resolution does deteriorate although we have seen worse cases. Distortion stays within the accepted limits, with figures of –0.3% (barrel) at the 55mm end and 1.41% (pincushion) at the 200mm point. The new digital coating that Sigma applies to all of its lenses has enormous benefit in reducing flare and ghosting, with no problems encountered.

Nowhere throughout the entire zoom or aperture range is there any significant evidence of chromatic aberrations, which is commendable, but this does seem to have been achieved at a slight expense to contrast that lacked slightly in some areas. The contrast however, is much more easily remedied in software and, although subject dependent, was not that noticeable to the eye.