Sigma 18-125mm f/3.5-5.6 DC

This lens from Sigma has been created specifically for cropped sensor digital single lens reflex cameras (dSLR’s) with sensors in the region of APS-C size. It is given the DC nomenclature for this reason. Newly designed by Sigma as a wide angle to short-medium telephoto for use as a general purpose, walk-around lens, we take a look at how it performs.

Specifications

• Focal length 18-125mm
• Aperture f/3.5-5.6
• Angle of view 69.3-11.4°
• Filter size / type 62mm
• Construction Elements/groups 15 elements in 14 groups
• Focusing type
• Closest focus 0.5m
• Weight 0.385kg
• Dimensions (Dia x length) 70x77.7mm
• Mounts available Sigma, Canon, Nikon, Minolta, Pentax , 4/3rds
• Tripod bush No
• Price £229.99

Build and Handling
This lens is supplied boxed and includes a petal hood and documentation in the carton. From the mount, which is metal, going forward there is a short area on which is mounted the AF/MF switch where required. This is followed by a good size zoom ring marked at 18, 24, 28, 35, 50, 70, 100 and 125mm. Two thirds of the ring is covered with a nice feeling ribbed rubber grip that provided good non-slip. A zoom lock is provided to keep the lens from extending, but we did not find this a problem with the lock disengaged. Forward of this and half the width was the manual focus ring marked with a distance scale in metres and feet and a 10mm band of ribbing. It required less than a quarter turn to operate from one extreme to the other and no sloppiness was detected.

On zooming, the front element came out of the barrel some 52mm (2”) and there is no further extension during focusing. The front element does not rotate during either operation, facilitating the easy use of filters. Focussing is quick enough for most purposes short of extreme action and although not silent was not over noisy and did not sound as though it was grinding into position as some lenses do. The petal hood, a bayonet fit, clicked into position positively and gave confidence that it would stay in place. Torque on the zoom ring feels right and it is smooth in operation. The lens is also one of the few third party lenses available in 4/3rds fit.

Optical Quality
With a zoom ratio of just under 7:1 this lens covers a good range without going to the extremes of the 10+ times zooms. As with most wide ranging zoom lenses, the performance is better at the shorter end with some fall-off in performance as focal length is extended. However, the fall-off in this lens is kept to a minimum with a good starting point at the short end. Distortion is well controlled for the class of lens, with minimum barrel at the short end moving to negligible pincushion at the longer length. Sigma have learnt well how to control chromatic aberrations and none of their new designs have suffered from the anomaly. That includes this design, which showed no significant signs throughout the range.

The lens has a useful focal range for a walk around lens. This shot, taken at 51mm and 1/500sec at f/8 on a Sigma SD10 is around the middle of the range.	1/100sec and f/8 produced this shot with the lens set at 30mm. Even at this size, you can see the detail is well recorded and contrast is up to the job on a drab subject.
	This shot was taken from the same spot as the harbour scene, but turning slightly and zooming to the full 125mm. Again f/8, but this time at 1/60sec handheld, showing it is a comfortable lens to use.

Click on each comparision photo below to view full size versions

18-125mm set at 18mm and f/8	18-125mm set at 125mm and f/8
18-125mm set at 18mm and f/3.5	18-125mm set at 125mm and f/5.6

Below is our lens test data. To find out how to use these graphs look at this article: How we test lenses

Verdict
As a walk-around lens, this design from the Sigma stable scores well over the normal offering of ‘kit’ lenses, giving extended focal length at the long end and improved performance at the wide end. The reduced need for lens changes on the digital SLR’s that it is made for ensures less chance of the dreaded dust getting at the sensor whilst, at the same time, the light weight and compact size will reduce neck ache after long days carrying it around. It’s ability to cover everything from landscape through portraits to short telephoto work makes and ideal addition to the camera kit.

In summary, the positive points of the Sigma 18-125mm f/3.5-5.6 DC lens are
Compact size and weight
Good build quality
Out-performs most ‘kit’ lenses especially at the wide end.
Good range of mounts available.

Negative points are:
Drop in performance at longer focal lengths

Check the latest price of the Sigma 18-125mm f/3.5-5.6 DC lens here

Test by Ian Andrews www.wildaboutkent.co.uk

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