Sigma AF 12-24mm f/4.5-5.6 EX DG - Review / Lab Test Report
Lens Reviews - Sony Alpha/NEX (APS-C)
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Review by Klaus Schroiff, published February 2008

Special thanks to Konrad Kandler for providing this lens for testing!


The Sigma AF 12-24mm f/4.5-5.6 EX HSM DG is of three ultra-wide zooms made by Sigma - obviously a primarily playing field for the company. The 12-24mm EX is a full format lens and within its range it is currently unique in Sony Alpha mount. In fact there isn't even a (mass production) rectilinear SLR fix-focal this wide. Quite an achievement! On an APS-C DSLR the specifications are not all that impressive anymore but the field-of-view is still equivalent to a classic 18-36mm lens so even here it keeps its ultra-wide character.

Due to the extreme design Sigma had to choose a very protruding front element so there's no front filter thread by default. However, when attaching the lens cap holder there is a option to mount a filter here (82mm). At 12mm this causes slight edges shading so front filters can only be used from about ~14mm. There's a gelatin filter slot at the rear of the lens (useful for color filters for B&W photography).

The build quality of the lens is very impressive and among the best what Sigma has to offer. The typical EX finish (smooth crinkle style) feels very pleasant and the zoom and focus control rings operate very smooth. Unlike the Canon and Nikon variant the Sony Alpha variant does still rely on the conventional focusing system driven by the camera (via a slotted drive screw). The AF produces a moderate degree of noise during operations but it is very fast and reasonably accurate - although AF speed does hardly matter for an ultra-wide angle lens.

Equiv. focal length18-36 mm (full format equivalent)
Equiv. aperturef/6.8-f/8.4 (full format equivalent, in terms of depth-of-field)
Optical construction16 elements in 12 groups inc.4 SLD and 3 aspherical elements
Number of aperture blades6
min. focus distance0.28 m (max. magnification ratio ~1:7.1)
Dimensions87 x 103 mm
Weight600 g
Filter size82 mm (non-rotating - see issues above)
Hoodbuilt-in, petal-shaped
Other featuresgelatin filter slot