Sigma's 70-300mm f/4-5.6 DG OS telephoto zoom lens is targeted at amateur photographers who require an affordable long-zoom lens to complement, say, an 18-55mm or 18-85mm kit lens on their DSLR. Usable with both 35mm cameras (and ‘full-frame' DSLRs) and DSLRs with APS-C sized sensors, this lens can be used for subjects as diverse as portraiture, sports, wildlife and travel photography.
This isn't the only 70-300mm lens in Sigma's catalogue; merely one of the latest. Others in the list include the older and pricier 70-300mm APO DG Macro and the 70-300mm f/4-5.6 DG Macro, each of which was recently updated for Nikon cameras.
The Sigma 70-300mm f/4-5.6 DG OS telephoto zoom lens, shown without the supplied lens hood and end caps. (Source: Sigma.)
The DG (Digital) tag refers to a special optical design for optimising performance with digital camera sensors - although this lens is also usable on film SLRs. As well as including optical coatings for improving light transmission, Sigma has concentrated on correcting distortion and aberrations, particularly chromatic aberration, which is conspicuous with digital cameras.
OS refers to Optical Stabilisation. The Sigma system uses two sensors inside the lens to detect vertical and horizontal movements then moves a dedicated stabilising lens group to compensate and provide a steady image in the viewfinder and at the sensor. In its more sophisticated lenses, Sigma provides separate stabilisation modes for detecting vertical and horizontal shake. However, in this lens there's only one mode, which provides both vertical and horizontal detection and correction. Up to four stops of shutter speed advantage are claimed for the 70-300mm f/4-5.6 DG OS lens.
As with other Sigma lenses, the 70-300mm f/4-5.6 DG OS will be offered in Canon, Nikon, Pentax, Sigma and Sony mounts. For Pentax and Sony cameras, which have body-integrated stabilisation systems, the built-in OS function can provide a steady image in the viewfinder or it can be switched off via a slider on the side of the lens barrel.
The optical design of the Sigma 70-300mm f/4-5.6 DG OS lens, with the SLD element shown in solid blue. (Source: Sigma.)
For its focal length range, this is a fairly compact and lightweight lens. The optical design comprises 16 elements in 11 groups and includes one SLD (Special Low Dispersion) glass element for correcting all types of aberrations. Sigma has applied a Super Multi-Layer Coating to subdue flare and ghosting and provide high contrast images throughout the focal length range. The nine-bladed iris diaphragm closes to a circular aperture for attractive bokeh.
Build quality is well above average for the price point. The barrel feels solid and fit and finish are very smooth. Parts of the barrel carry an attractive matte black finish that is pleasant to hold. The same material has also been used for the supplied cylindrical lens hood, which fits on with a bayonet mounting and adds approximately 43 mm to overall length. A stainless steel mounting plate provides a secure connection to the camera body.
For this review, our tests were conducted with a Canon EOS 5D body, which allowed us to use the lens at its designated focal length range. With a Canon ‘APS-C' DSLR, the effective focal length range would be 112-480mm; on Nikon, Pentax and Sony bodies with ‘APS-C' sensors, it is 105-450mm.
The zoom ring is a 50 mm wide band roughly mid-way down the lens barrel. It has a broad, ridged rubber coating that provides a secure grip. The leading edge is engraved with white, easily-read focal length marks for 70, 100, 135, 200 and 300mm focal length settings. As you move through this range, the maximum and minimum apertures change, as shown in the table below.
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Focal length
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Maximum aperture
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Minimum aperture
|
|
70mm
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f/4.0
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f/22
|
|
100mm
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f/4.5
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f/25
|
|
135mm
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f/5.0
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f/29
|
|
200mm
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f/5.6
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f/32
|
|
300mm
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f/5.6
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f/32
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The focusing ring lies on an inner barrel and protrudes 28 mm towards the front of the lens. It carries a 9 mm wide ridged grip, behind which feet and metres are engraved in white, ranging from 1.5 metres (the closest focusing distance) to infinity. The inner barrel rotates a little during focusing so re-adjustment of angle-critical attachments (such as polarisers) is necessary. No rotation appears to be associated with zooming.
The left side of the lens barrel behind the zoom ring carries two slider controls. The top one is a simple AF/MF switch, while the second slider switches the OS stabiliser on and off. Unlike Sigma's more up-market lenses, the 70-300mm f/4-5.6 DG OS is not equipped with an HSM (Hyper-Sonic Motor) so autofocusing is not super-fast. However, it's certainly fast enough to cope with most moving subjects, as can be seen in the Sample Images section at the end of this review. Don't expect silent autofocusing, although it's relatively quiet for the type of motor used.
Handling
The review lens felt comfortable on the EOS 5D body we used for our tests. Both focusing and zoom rings showed no slack yet moved smoothly and positively. No zoom lock is provided - and none appears to be required since the review lens showed no tendency to extend when carried pointing downwards. All controls are located within easy reach and the sliders, although small, are easy to adjust.
The zoom ring moves through roughly 90 degrees of rotation and we found the markings on the lens barrel to be accurate for the indicated focal length settings. The focusing ring can be moved through approximately 30 degrees in MF mode, making precise manual focusing straightforward.
Although no ‘macro' settings are provided, it is possible to shoot attractive close-ups of flowers and other small subjects - provided the camera-to-subject distance required is greater than 1.5 metres.
Performance
Most test shots taken with the review lens on the EOS 5D body were sharp and detailed and the autofocusing system was able to keep pace with the 5D's burst mode when we were shooting moving subjects. We noticed occasional hunting when light levels were low but overall response times were good for a ‘consumer' lens.
Imatest showed the lens to be capable of matching the resolution of the 5D's sensor - and exceeding it at times. It also showed excellent flatness of field through very little difference in centre and edge resolution across the aperture ranges for each focal length setting.
We obtained the best results with the 70mm focal length setting and (surprisingly) the lowest resolution figures at 200mm. (Lack of space in our test set-up prevented us from measuring performance at 300mm.) The graph below shows the results of our Imatest tests.
Lateral chromatic aberration was consistently in the ‘negligible' band, just venturing into the ‘low' category with the widest apertures at the 135mm and 200mm focal length settings and mid-way along the 70mm aperture rang. Interestingly it was consistently very low throughout the aperture range with the 100mm focal length setting. The graph below shows the results of our Imatest tests. (The red line marks the boundary between 'negligible' and 'low' CA.)
Overall, the level of rectilinear distortion in this lens is very low and better than average for a 4x zoom lens. We found no evidence of barrel distortion at either 70mm or 100mm and only slight pincushion distortion at 135mm and 200mm. Neither would affect normal photography.
Vignetting (edge darkening) could be seen in shots taken at the maximum aperture at all focal length settings. However, it was less than 0.7EV with the 300mm focal length and less than half a stop at 70mm. Stopping the lens down one or two f-stops eliminated the problem.
Flare was almost a non-issue when the lens hood was in place, although very slight veiling could be seen in some shots taken with strong backlighting. Bokeh at wide apertures was quite attractive - even when there was plenty of background detail to subdue.
Buy this lens if:
- You want an affordable and capable zoom lens to extend the reach of a standard kit lens.
- You'd like a versatile lens that can be used for subjects as diverse as portraits, landscapes and wildlife.
Don't buy this lens if:
- You require a fast, professional quality lens for low-light photography.
- You need close focusing and macro capabilities.
- You make frequent use of polarisers and graduated filters.
IMATEST GRAPHS
SAMPLE IMAGES
The 70mm focal length setting with the review lens on the EOS 5D, which has a 36 x 24 mm sensor.
The 300mm focal length setting with the review lens on the EOS 5D.
The 70mm focal length setting with the review lens on the EOS 40D, which has a 22.2 x 14.8 mm sensor (1.6x crop factor).
The 300mm focal length setting with the review lens on the EOS 40D.
Close-up shot showing bokeh:225mm focal length, ISO 100, 1/83 second at f/5.6.
Crop from the above image.
Action shot to show AF responsiveness: 180mm focal length, ISO 100, 1/790 second at f/5.6.
Crop from the above image.
Shot showing narrow depth-of-field: 300mm focal length, ISO 100, 1/99 second at f/5.6.
Crop from the above image.
Animal portrait showing detail: 300mm focal length, ISO 100, 1/250 second at f/5.6.
Crop from the above image.
Portrait: 160mm focal length, ISO 100, 1/25 second at f/5.
Wildlife: 300mm focal length, ISO 100, 1/99 second at f/6.4.