Sigma 8-16mm f/4.5-5.6 DC HSM lens

The lens is equipped with a built in lens hood. It comes with a front cap, a ring to mount the front cap and a rear cap.

The lens measures 106 by 75 millimetres (4.2 in × 3.0 in) and weighs 555 grams (1.224 lb). It has a bulb-like aspherical lens, similar to notable wide-angle and fisheye lenses such as the Nikon AF-S NIKKOR 14-24mm f/2.8G ED, Nikon AF DX Fisheye-Nikkor 10.5mm f/2.8G ED, or Tokina AT-X 107 DX AF 10-17mm f/3.5-4.5 fisheye lens.[6] Because of the shape of front element, it is not compatible with many filters, including UV filters, but the frontal exposure is rectified by a petal-shaped lens hood element.[5] Because the lens has a permanent lens hood affixed, it comes with a friction-fit aluminum element, variously described as a sleeve, ring or shroud,[3] that surrounds the hood to enable the placement of a front cap on the lens.[5] PC Magazine's Jim Fisher says the lens is relatively large and heavy;[8] A reviewer at photozone.de says that for a wide-angle lens the dimensions are unusually narrow but long.[5]

The sleeve is threaded, making it compatible with 72mm filters, but vignetting is severe with the sleeve in place.[4] The construction is plastic although the lens' rear mount is metal.[3][6] The distance meter is recessed inside a window, but no depth of field meter or infrared index is present.[3] The 7/8" zoom ring is made of raised rubber ridges and operates over a 75 degree turning radius. The focus ring is similarly constructed with more closely spaced ridges and a 100 degrees of turning action. The ridges of both rings are parallel to the lens.[3]

The only physical controls on the lens are the AF/MF toggle switch and the two rings, controlling the zoom and focus.[8] The lens does not have image stabilization. This is common for wide-angle photography which can be performed well using hand-held techniques.[6] Over the range of focal lengths, the minimum and maximum aperture vary.[3]

Canon Rebel T3i with Sigma 8–16mm f/4.5–5.6 DC HSM lens. Bottom with sleeve and cap

The lens features a hypersonic zoom motor for its autofocus, which is considered to be a fast and quiet design.[5][6] In addition, manual override is allowed in the single-shot autofocus mode.[5] The lens, which focuses internally, has one of the lowest maximum magnification measurements in its class (which includes the Canon 10–18mm and 10–22mm, Sigma 10–20mm f/3.5 and Sigma 10–20mm f/4–5.6 EX DC HSM, Tamron 10–24mm f/3.5–4.5 DI II, Nikon 10–24mm f/3.5–4.5G ED AF-S DX, and Tokina 11–16mm f/2.8 AT-X Pro DX lenses).[3][4] The lens' autofocus feature is not functional with Pentax ist* series and K100D DSLR cameras that do not support hypersonic zoom mechanics.[1] The lens is capable of focusing from infinity to minimum focusing distance and back in under a second: so micro focusing is rapid.[3] However, because of the narrow focus range (0.13x) the lens is not suitable for macro photography.[3]

The lens exhibits significant distortion in keeping with the problems of wide-angle lenses.[5] The complex barrel distortion is approximately 2.9% at 8 mm focal length but is fairly insignificant as the focal length is raised above 12 mm, according to Photozone.de.[5] PC Magazine reports 3.1% distortion at 8 mm and 0.7% at 12 mm.[8] It also reports that distortion switches to pincushion distortion of 1.4% at 16 mm.[8] SLAR Gear reports that the point of convergence between barrel and pincushion is about 13 mm.[3] Foreground subjects seem abnormally large compared to similar background subjects with this lens.[4]

By combining the wide angle focal lengths with narrow apertures, the lens provides strong depth of field rather than making blurred backgrounds.[4] The lens is constructed with a hybrid aspherical lens that when combined with two glass mold elements provides excellent correction for distortion as well as astigmatism.[1]

As all lens systems, natural vignetting (gradual reduction of an image's brightness from the center towards the periphery) is present due to Lambert's cosine law – this becomes more pronounced at shorter focal lengths.[5] Wide open at 8 mm, about 0.75 EVs of shading are apparent at the corners, while at 16 mm only about 0.25 EV of shading is noticeable when comparing the corners to the center.[3] For most of the focal length range of the lens, there is between a half stop and third stop of corner shading.[3] Alternatively, stopping down to higher f-numbers lessens vignetting.[9]

The restriction of the field of view due to the build in lens hood becomes visible on a full-frame digital SLR (left to right: 8 mm, 12 mm and 16 mm focal length).

The lens is equipped with a full-frame digital SLR-compatible mount allowing the usage of both APS-C sized cameras and formats larger than APS-C – the build in lens hood however visibly restricts the field of view (FOV) on formats larger than APS-C – see example above.[1][3] The FOV in APS-C sized cameras is further restricted at shorter focal lengths if the front cap adaptor ring is not removed – see example below.[5]

If the front cap adaptor ring is not removed, the field of view becomes restricted even on an APS-C digital SLR camera (left to right: 8 mm, 10 mm, 12 mm, 14 mm and 16 mm focal length).

The lens' modulation transfer function (MTF) metrics for its image resolution (sharpness) were described as "surprisingly impressive...throughout the entire zoom range" by Photozone.de.[5] The sharpness, in terms of line widths per picture height (LW/PH), is most uniform at 8 mm (especially near the f-number of 8 where it is even throughout the image) with strong numbers at the center, borders and corner. Higher focal lengths were less impressive.[5] Optical tests were consistent with lab results pointing to excellent sharpness.[10] However, exposure testing seems to belie the stated f-number capabilities of the lens, since stopping down from widest aperture did not change results, according to Gietler.[10]

At its widest aperture, the sharpness does not meet the 1800 threshold at either 8 mm (1572, f/4.5) or 12 mm (1356, f/5), but at 16 mm (f/5.6) it achieves over 2000 lines per picture height. However, stopping down improves the sharpness at all focal lengths, according to PC Magazine. At 8 mm, 1800 is reached at f/8, while at 12 mm it is still only at 1509 by f/8.[8] The image quality is asymmetric with better performance on the right side.[4] At 8 mm and f/4.5, it has 1 blur unit in the center and 1.5 in the corners.[3] Although the images are slightly sharper at f/5.6, SLR Gear claims sharpness declines significantly at f/11 to almost 2 blur units with further stopping down increasing blur to 3.5 at f/22.[3] At the longer focal lengths for this lens, stopping down to f/29 yields a 5 blur unit result.[3]

The lens is the first that incorporated Sigma's FLD glass elements, designed to correct color aberrations like fluoride glass does.[5] Chromatic aberrations are indeed superior to earlier Sigma wide-angle lenses. In fact, although they might be noticeable at 100% image magnification, they are not at the magnifications now common with prints relative to the number of megapixels that images are commonly captured at.[5] According to Sigma's website, Super Multi-Layer Coating reduces flare and ghosting.[1] As one zooms out with this lens chromatic aberration becomes significant at the corners.[3]

The aperture stop-down focal lengths make the lens a laggard among wide-angle lenses.[4] Thus, it is not strong at gathering light for stop action photography. However, DSLR cameras have improved at higher ISO settings.[4] However, wide-angle photography (below 16mm) continues to need stronger lighting than is possible by built in flashes if trying to make up for low light situations.[4]

At 8 mm and 16 mm, respectively, the lens is able to focus on an area 12.25 inches (31.1 cm) and 7 inches (18 cm) in width.[6] Although the official close focus distance is 24 centimetres (9.4 in),[1] Scott Gietler reported that by using the spot-focus mode, rather than multiple focus points, he was able to achieve a 3 inches (7.6 cm) minimum working distance (glass to subject).[6]

The lens is useful for deliberative shots by landscape photographers and other skilled artists.[8] The challenge of the vast field of view may be overcome by some casual users.[8] Car photographers benefit from the new perspective of this lens.[4] The lens was a 2010 American Photo Editor's Choice.[1]

• Commons: Pictures taken with Sigma 8-16mm f/4.5-5.6 DC HSM lens
• Official Sigma website
• Digital Photography Review
• Underwater photography review
• Photozone test on Canon EOS 50D
• Photozone test on Nikon D7000