Zeiss Distagon T* 24mm f/2 ZA SSM (SAL-24F20Z) - Full Format Review / Lab Test
Lens Reviews -
Sony Alpha (Full Format)
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Review by Klaus Schroiff, published December 2010
Lens kindly provided by Dieter Scherk!
The Zeiss Distagon T* 24mm f/2 ZA SSM (SAL-24F20Z) is a moderate ultra-wide angle lens for the Sony Alpha system. It is a full format design and as such highly interesting for Alpha 850/900 users so this review focuses on its native format.
According to the Zeiss naming convention "Distagon" refers to a "retro-focus" lens based on an asymmetrical design. The asymmetry in necessary to provide the required space for a SLR mirror. The first Distagon lens was introduced in 1953 - a 60mm f/5.6 for the Hasselblad 1000F. The design evolved over time, of course, and it's no longer just used by Zeiss but across the whole industry.
Regarding its max. aperture of f/2 it doesn't really qualify as "ultra large aperture lens" anymore but this "limitation" may be actually a quite smart decision upon 2nd thought. Thanks to the more moderate aperture the Zeiss lens is a little cheaper than its f/1.4 rivals made by Canon and Nikon and - probably more important than that - it is far simpler to design. At f/1.4 the manufacturers are struggling to overcome heavy aberrations (optical defects) in order to provide some sort of usable image at max. aperture whereas the optical situation is far more forgiving when starting at f/2.
The build quality of the lens is nothing short of outstanding. The lens body is completely made of metal and that's including the smoothly operating fluted focus ring. The physical length of the lens remains constant at all focus setting and there's also no moving inner lens tube. Distagon lenses feature a rear-focus design (IF - inner focusing) so the front element does not rotate. On the downside Sony does not mention any weather sealing which may be a little disappointing for some. The petal-shaped lens hood is made of good quality plastics.
The Zeiss lens features Sony's "supersonic motor" (SSM), an AF drive based on ultrasonic waves similar to Canon's USM and Nikon's Silent Wave drive. The AF is both very fast and virtually silent. DMF ("Direct Manual Focusing") is supported.
|Optical construction||9 elements in 7 groups inc. 2x aspherical + 2x ED elements|
|Number of aperture blades||9 (rounded)|
|min. focus distance||0.19m (max. magnification ratio 1:3.4)|
|Filter size||72mm (non-rotating)|
|Hood||petal shaped, supplied|