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Review by Markus Stamm, published March 2013
Sigma offers a trio of fast wide angle lenses, featuring focal lengths of 20, 24 and 28 mm. All three lenses share a maximum aperture of f/1.8 and a very short minimum focus distance, which allows for interesting and often dramatic perspectives of close subjects.
The lenses are designed for full frame cameras, but can of course be used on DX DSLRs, too. In this review we'll have a look at how the 28mm lens performs on our current DX test camera, the Nikon D7000, where it is the equivalent of roughly a 42mm f/2.8 lens. So, on DX the lens no longer behaves as a wide angle, but almost as a standard lens.
Due to the similarities of the lenses, the three reviews share large portions of text.
The lens belongs to the high end line of Sigma lenses (EX) and, from the mount to the focus ring, the build quality is actually on a high level. However, the frontmost part that holds the inner lens tube wobbles quite a bit.
The broad focus ring works as a clutch to switch between AF and MF mode. When pulled towards the camera, the lens can be focused manually, while the AF still works as long as the camera remains in AF mode. This way the lens allows for FTM (full time manual focusing), a feature usually only available on Nikon AF-S or Sigma HSM lenses with ultrasonic wave drives.
Typical for many Sigma lenses the focus ring of the EX 28 rotates in "Canon" style, which is the exact opposite of how these rings work on Nikkor lenses. If you're used to the Nikon way of focusing, the Sigma lens may be a challenge for your muscle memory. In addition, you'll have to remember that the focus assist in the viewfinder assumes a Nikon lens and consequently suggests the wrong direction of focus ring movement.
As can be seen in the product shots below, the lens extends a bit when focusing towards closer distance. The front element does not rotate, so using a polarizer is easily possible.
The lens has no built-in AF motor and relies on a drive screw operated by the camera (which makes it incompatible with entry-level DX cameras that no longer feature this screw drive). Thanks to a rather short focus path the AF works quite fast.
|Equiv. focal length||42 mm (full format equivalent)|
|Equiv. aperture||f/2.7 (full format equivalent, in terms of depth-of-field)|
|Optical construction||10 elements in 9 groups including 2 aspherical elements|
|Number of aperture blades||9|
|min. focus distance||0.2 m (max. magnification ratio 1:2.9)|
|Dimensions||83.5 x 80 mm|
|Filter size||77 mm (non-rotating)|
|Hood||petal-shaped, bayonet mount (supplied)|
|Other features||Lens provides distance (D) information to the camera|