Sigma 120-400mm f/4.5-5.6 DG OS HSM

Gary Wolstenholme takes a look at this 3.3x super-telephoto zoom from Sigma with optical stabilisation.

Available for around £672, this 120-400mm optic from Sigma promises to be a well-specified super-telephoto option for those without a four-figure budget. For that price you get optical stabilisation and a silent focusing motor that allows manual focus adjustments to be made at any time.

Tokina also manufacture a budget telephoto zoom ending at 400mm. Their AT-X 80-400mm f/4.5-5.6 lacks the silent focusing motor and optical stabilisation of the Sigma, but only costs around £480.

Canon's ever-popular 100-400mm f/4.5-5.6L is their closest equivalent to this Sigma. Apart from being a little wider at the short end, the Canon's spec is very similar to this Sigma having both optical stabilisation and a silent focusing motor but costs a fair bit more at around £1220. Those just looking for the 400mm end may also consider Canon's 400mm f/5.6L, which lacks image stabilisation and costs £1094, but has an enviable reputation for the quality it can deliver.

The 80-400mm f/4.5-5.6D AF VR lens is Nikon's closest equivalent. This lens costs around £1190 and offers more width at the short end and Vibration reduction, but lacks a silent focusing motor. For those with money to burn, Nikon also offer a 200-400mm f/4 optic, which has all the bells and whistles, such as VR and silent focusing, along with professional weather-sealed build quality for the princely sum of around £4995.

Sony's 70-400mm f/4-5.6 G SSM costs around £1430 and sports silent focusing and weather-sealed build quality, but no image stabilisation. As all Sony DSLRs already contain Steady Shot stabilisation in the body, this may render in-lens stabilisation unnecessary.

Pentax don't currently manufacture any lenses longer than 300mm, which means owners of Pentax cameras after a bit of extra telephoto pulling power should be especially interested in third-party offerings like this.

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Handling and features
Although this lens doesn't carry Sigma's top of the range EX designation, the build quality and features are pretty similar to many of those lenses. Weighing 1640g, you'll certainly notice this lens in your bag if carrying it around all day. This is in part due to the sturdy build, which is finished in a matte powder coated effect, which looks very smart when new, but in use it can show marks quite easily.

A distance window is located near to the lens mount, but no hyperfocal markings are provided. As the lens uses Sigma's silent Hypersonic focusing motor, auto focus is fast and quiet in good light. In poorer lighting conditions it does tend to hunt around, especially at the longer end of the zoom range. With a bit of care and attention this lens should be plenty fast enough at focusing to keep up with erratic subjects such as birds in flight or sports. A large rubberised focus ring is located about halfway along the lens, which provides the perfect amount of resistance for making fine adjustments. The silent focusing motor also allows manual focus adjustments to be made at any time.

The large rubberised zoom ring is located towards the end of the lens barrel and the lens balances well on the D700 used for testing when fitted with the optional MB-D10 battery grip, but feels quite front-heavy when used without the grip. The zoom mechanism is actually quite loose and the lens does creep forward when tilted downwards when used on a tripod. A locking mechanism is provided to keep the lens at 120mm when being transported, which is useful as the lens tends to extend when taken from a bag without it.

Sigma's Optical Stabiliser promises to enable sharp shots to be taken at shutter speeds up to four stops slower than would normally be possible. Shooting at 400mm, I am able to take sharp images hand held consistently at 1/100sec, which is two stops slower than what would normally be regarded as the ideal shutter speed. Pushing things further, I was able to take sharp images roughly two thirds of the time at 1/50sec and about a quarter of the time at 1/25.

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Performance
Unlike many other telephoto zoom lenses which perform at their best at the shortest focal length, this lens has it's sweet spot somewhere in the middle of the zoom range.

Shooting wide open at 120mm the sharpness in the centre is already very good. But the quality towards the edges of the frame lags behind somewhat. Stopping the lens down improves the quality towards the edges of the frame and reaches its peak at f/11. Here the resolution recorded across the frame is very good.

Zooming to 200mm results in better sharpness towards the edges than wide open at 120mm, whilst still retaining the very good sharpness in the centre of the frame. At this focal length, peak quality across the frame is achieved at f/16.

At 400mm, the quality across the frame drops off noticeably. At f/5.6 the sharpness in the centre is reasonable and only fair towards the edges. Peak quality across the frame is achieved between f/11 and f/16 at this focal length where the sharpness in the centre is good and the edges are not too far behind.

Resolution at 120mm	Resolution at 200mm
Resolution at 400mm	How to read our graphs The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple. For this review, the lens was tested on a Nikon D700 using Imatest.

Due to Sigma's use of three SLD low dispersion glass elements, chromatic aberrations are well controlled and should not pose any issues, even on close inspection. At its worst, fringing can cover an area of just under half of a pixel width, which is good performance for a super-telephoto zoom.

Chromatic Aberrations at 120mm	Chromatic Aberrations at 200mm
Chromatic Aberrations at 400mm	How to read our charts Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more. For this review, the lens was tested on a Nikon D700 using Imatest.

Falloff of illumination toward the corners of the frame is well controlled at 120mm. Here the corners are only 0.972 stops darker than the image centre. Stopping down to f/8 results in visually uniform illumination here. At 400mm and f/5.6 falloff of illumination is a little stronger with the corners being 1.27 stops darker than the image centre. At this focal length the lens needs to be stopped down to f/11 for visually uniform illumination.

Only slight barrel distortion of 1.27% was detected by Imatest at 120mm and only slight pincushion distortion of 0.872% at 400mm. Both these levels are so low that they should pose few issues for most people, but if the slight curvature does need to be corrected, it should be straightforward to correct, as the distortion pattern is uniform across the frame.

Click on the thumbnails for a high resolution image.
At 120mm, sharpness in the centre is already very good from wide open, but the lens needs to be stopped down to improve the quality towards the edges of the frame. ISO200, 1/400, f/8, 120mm		At 400mm the lens is less sharp than at shorter focal lengths, but sharpness in the centre of the frame is still good when stopped down. ISO200, 1/160, f/8, 400mm

When using the lens without the supplied petal shaped hood, it can be quite prone to flare and loss of contrast with strong light sources outside of the frame. Luckily the supplied hood does a great job of reducing the chances of this becoming an issue. Strong light sources within the frame will also cause a noticeable loss of contrast and occasionally flare, so can may need to be taken in those circumstances.

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Verdict
Being priced at £675, this lens represents a good value choice for those looking for a super-telephoto lens, without the extortionate price tag associated with some camera manufacturer's own lenses in this range. For it's price, it has excellent build quality and a good range of useful features, such as Optical Stabilisation and silent focusing, but some aspects of handling could still be improved, like the looseness of the zoom mechanism.

The lens does have some limitations, but so long as you are aware of these, it is still capable of producing very good quality images in the right hands.

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Pros
Priced well
Good build quality
Optical Stabilisation
Silent focusing with full-time manual override

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Cons
Prone to flare when used without the supplied lens hood
Loose zoom mechanism suffers with zoom creep
Hunts for focus in low light conditions

FEATURES
HANDLING
PERFORMANCE
VALUE FOR MONEY
OVERALL

Sigma 120-400mm f/4.5-5.6 DG OS HSM: Lens specification

Price	£675.00
Contact	www.sigma-imaging-uk.com
Filter size	77mm
Format	Full-frame
Construction	21 elements in 15 groups
Angle-of-view	20.4 - 6.2 degrees
35mm equivalent focal length (on APS-C body)	180-600mm
Internal focusing	Yes
Image stabilisation	Yes
Minimum focus	1.5m
Maximum aperture	f/4.5-5.6
Minimum aperture	f/22-32
Weight	1640g
Size	92 x 203mm
In the box	Lens Hood Fitted Padded Case Front and Rear Caps Instruction Manual 1 Year Warranty Card

The Sigma 120-400mm f/4.5-5.6 DG OS HSM costs around £675 and is available from Warehouse Express here:

Sigma 120-400mm f/4.5-5.6 DG OS HSM for Canon
Sigma 120-400mm f/4.5-5.6 DG OS HSM for Nikon
Sigma 120-400mm f/4.5-5.6 DG OS HSM for Sony
Sigma 120-400mm f/4.5-5.6 DG OS HSM for Pentax
Sigma 120-400mm f/4.5-5.6 DG OS HSM for Sigma

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