The Photo Times: Sigma 24-105mm f/4 DG (OS) HSM Art Lens

In summary

The 24-105mm focal length is a versatile range on cameras with 36 x 24 mm sensors. It’s less attractive on cameras with APS-C sized chips, covering the equivalent of 36-157.5mm on Nikon, Pentax and Sony cameras and 38.4-168mm on Canon bodies.

On ‘full frame’ cameras, this lens would be an excellent everyday lens, covering everything from landscapes to portraiture and event and reportage photography. The constant f/4 maximum aperture is fast enough to suit most of these applications and still provide decent out-of-focus blurring, particularly at longer focal length settings.

While not hugely better than others in its class, Sigma’s 24-105mm f/4 DG HSM OS Art series lens is much more affordably priced. Its build quality and excellent centre-of-frame resolution make it worthy of consideration, particularly for owners of ‘full frame’ DSLRs who want a capable general-purpose lens.

Sigma is obviously targeting Canon users with this lens by offering the same basic specifications as the popular Canon EF 24-105mm f/4 USM L IS, which Canon has been slow to update. The Sigma lens is a bit larger and heavier than the Canon alternative and feels more solidly built. Superficially, it’s also better finished and more comfortable in the hands.

However, Canon owners should be aware that in-camera Peripheral Illumination Correction data for this lens is not available, as it is for Canon lenses. We don’t see this as a serious problem since vignetting is relatively easy to correct with decent editing software. However, given the strength of the vignetting at wide apertures, for photographers who don’t edit their images, this issue may be a ‘deal-breaker’.

Since neither Nikon nor Sony has lenses that cover the 24-105mm zoom range, this lens provides an attractive alternative to the significantly more expensive AF-S Nikkor 24-70mm f/2.8G ED, or AF-S Nikkor 24-120mm f/4G ED VR for Nikon FX camera owners, or the very pricey Carl Zeiss Vario-Sonnar T* 24-70mm f/2.8 ZA SSM, the only option for owners of Sony DSLRs.Â

Full review

Sigma’s 24-105mm f/4 DG OS HSM Art lens is a premium lens designed for full frame cameras’, although it can also be used on cameras with APS-C sensors. As an ‘Art’ lens, it’s designed to offer ‘sophisticated optical performance’ and meet the needs of creative photographers. It is available in mounts for Â Canon, Nikon, Sigma and Sony, the latter without stabilisation as Sony Alpha DSLRs have body-integrated stabilisation.Â

Sigma’sÂ 24-105mm f/4 DG OS HSM Art lens, shown with the supplied lens hood attached. (Source: Sigma.)

The optical design (shown below) consists of 19 elements in 14 groups and includes three aspherical elements, two elements made from FLD (fluorite-like low dispersion) glass and two SLD (Special Low Dispersion) elements, as shown in the diagram below. Nine iris blades close to create a rounded diaphragm that creates attractive background blurring (bokeh).

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The diagram above shows the positions of the exotic elements in the optical design of the lens. (Source: Sigma.)
Â This lens features a number of Sigma’s proprietary technologies, including the Hyper Sonic Motor (HSM) ultrasonic autofocusing drive, optical stabilisation (OS) and Super Multi-Layer Coating technology which suppress reflections between the image sensor and lens surfaces to minimise flare and ghosting.Â Â (Sony mount lenses don’t include OS as sensor-shift stabilisation is included in all camera bodies.)

The use of Thermally Composite Material (TSC) reduces overall size and weight. As part of the new Global Vision design, this lens is compatible with the Sigma USB dock and software, which allows further customisation. It’s also eligible for the new Mount Conversion Service.Â The lens is supplied with front and end caps plus a petal-shaped lens hood and a soft case.

Who’s it For?
The 24-105mm focal length is a versatile range on cameras with 36 x 24 mm sensors. It’s less attractive on cameras with APS-C sized chips, covering the equivalent of 36-157.5mm on Nikon, Pentax and Sony cameras and 38.4-168mm on Canon bodies.

The design and pricing of this lens is very competitive, as shown in the table below, which compares its key specifications with their fastest close equivalents from the leading DSLR manufacturers.

Outdoor photographers should note that this lens is not weatherproof â€“ despite its excellent build quality. This may reduce its appeal to some photographers.

Canon’s L-series lenses (including the EF 24-105mm f/4L IS USM) include gaskets and O-rings to keep dust and moisture out. Most Nikon zoom lenses with a maximum aperture of f/2.8 are weather-resistant (including the Nikkor 24-120mm f/4 VR and 24-85mm VR).Â So are Sony’s G-series lenses.

Build and Ergonomics
Â As mentioned above, the build quality of this lens is excellent. It also looks and feels smart, solid and professional and all adjustments are stable and smooth. No zoom lock is provided and none is required since the lens doesn’t slip when carried pointing downwards. Despite having two inner barrels, we found no evidence of any unsteadiness when the lens was zoomed in and out.

The overall length of the lens extends by approximately 45 mm as you zoom from the 24mm to the 105mm focal length. The front of the lens rotates through about 45 degrees during this adjustment. (The Canon EF 24-105mm f/4 USM L IS also rotates a little during zooming but less than the Sigma lens.)

Focusing adjustments are totally internal, enabling easy use of angle-critical attachments, such as polarisers. The zoom ring is located at the front end of the outer barrel. It’s 38 mm wide with focal lengths stamped on the un-ribbed front 7 mm section.

Indicators are provided for the 24, 35, 50, 70, 80 and 105 mm focal lengths. They line up against a white dot on the front section of the inner barrel. A 26 mm wide strip of thick rubberised ridges provides a secure and comfortable grip band. Engraved on the lower edge of the zoom ring are three numbers, which represent the last three digits of the release year for the lens.

The focusing ring is immediately behind the zoom ring. It’s about 13 mm wide and carries a slim ribbed grip band. There are ‘soft’ stops at each end of the distance range, coinciding with the settings in the distance window immediately behind the focusing ring.

Both the focusing and zoom rings were firm but very smooth to adjust. This lens has the same 45 cm minimum focusing distance as the Canon 24-105mm lens and the distance window displays measurements in metres and feet from 0.45 m to infinity.
Â Slider switches for the focusing and stabilisation modes are located to the left of the distance window in the same (non-moving) section of the lens barrel. The Focus mode switch selects between AF and MF and manual over-ride is available in the AF position. Like other Art lenses, this lens has the ‘A’ logo embedded in this section of the lens barrel.

The lower part of the barrel in this section is ribbed to make it comfortable and secure to hold. Behind this section, the lens slopes gently in towards the mounting plate. The only thing on this section is a white indicator dot for aligning the lens with the camera’s mounting plate.

Performance
Â Some performance aspects â€“ notably autofocusing and stabilisation â€“ were virtually identical to the Canon 24-105mm f/4 lens. This is understandable as both companies use similar technologies and it would be surprising if Sigma’s HSMÂ AF drive was faster and quieter than Canon’s USM drive â€“ or vice versa. The OS system in the review lens provided reliable shake compensation of Â about three stops, which is similar to Canon’s IS system in the 24-105mm f/4 lens.

Subjective assessments of test images showed them to be generally very sharp, with centre sharpness being very high at wide to mid-range aperture settings. Edge softening was noticeable at the widest apertures. Stopping down yields progressive improvements to peripheral sharpness.

Imatest confirmed our subjective assessments and showed the highest resolution to be at around f/5.6 with the 24mm focal length. Diffraction-limiting began to reduce resolution from about f/11, where the differences between centre and edge sharpness were fairly minimal. The graph below shows the results of our Imatest tests across the zoom and aperture ranges.

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Â Lateral chromatic aberration was reasonably well controlled and mostly in the ‘low’ range. In the graph of our Imatest results below, the red line separates negligible and low CA, while the green line marks the boundary of the ‘moderate’ CA band.

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Â Autofocusing was as fast and quiet as we’ve found with other Sigma lenses fitted with ultrasonic AF drive motors. Regardless of the light levels, the review lens was quick to lock-on and generally accurate.

Backlit subjects presented few problems and we experienced no loss of contrast or flare artefacts with strongly backlit scenes, regardless of the focal length setting. Vignetting was obvious in the corners of shots taken at f/4 with all focal lengths. Barrel distortion was noticeable at 24mm but changed to barely perceptibleÂ pincushion distortion at 105mm.

With a minimum close-focusing distance of around 45cm, this lens can only be useful for close-ups at longer focal lengths. The maximum magnification ratio of 0.22x (1:4.6) is adequate for larger subjects at 105mm.

Like other Art lenses we’ve reviewed, the nine-bladed iris diaphragm ensures background highlights remain circular and produced attractive bokeh at wide aperture settings. Out-of-focus highlights were almost circular in shape with some outlining visible in high-contrast transitions. Blurring in areas with low contrast was very smooth.

As part of Sigma’s Global Vision design, this lens is compatible with the new Sigma USB dock, which enables users to customise AF microadjustments to suit their personal preferences. Sigma’s MSRP for this product is US$79; it’s selling in Australia for around AU$85).

Conclusion
While not hugely better than others in its class, Sigma’s 24-105mm f/4 DG HSM OS Art series lens is much more affordably priced. Its build quality and excellent centre-of-frame resolution make it worthy of consideration, particularly for owners of ‘full frame’ DSLRs who want a capable general-purpose lens.

SPECS

Â Picture angle: 84.1 to 23.3 degrees

Â Minimum aperture: f/22

Â Lens construction: 19 elements in 14 groups (includingÂ aspherical lens element)

Â Lens mounts: Canon, Nikon, Sigma, Sony (without stabilisation)

Â Diaphragm Blades: 9 (circular aperture)

Â Focus drive: Hyper-Sonic Motor

Â Stabilisation: OSÂ Standard (approx. 3 stops compensation)

Â Minimum focus: 45 cm

Â Maximum magnification: 0.22x (1:4.6)

Â Filter size:Â 82 mm

Â Dimensions (Diameter x L): 88.6 x 109.4 mm

Â Weight:Â 885 grams
Â Standard Accessories: Front and end caps plus petal-shaped lens hood