The 50mm F1.4 EX DG HSM is the latest design from independent lens maker Sigma, announced in March 2008. It's a rare example of what is rapidly becoming an endangered species; an all-new, large maximum aperture, fixed focal length 'prime' lens, and (like Sigma's 30mm F1.4 DC before it) a hugely welcome addition to a market in danger of becoming saturated by identikit slow zooms. The 50mm focal length makes it a classic 'standard' lens for 35mm full-frame cameras, while on DSLRs with smaller format sensors it acts as a short 'portrait' telephoto, with an equivalent angle of view ranging from 75mm (on 1.5x 'DX' format) to 100mm (on Four Thirds DLSRs). The fast maximum aperture offers several key advantages over zooms, including the ability to isolate a subject by selectively blurring the background, the option to shoot in low light whilst maintaining reasonably high shutter speeds (ideal for indoor photography without flash), and the provision of a bright viewfinder image for composition.
Of course all of the major camera manufacturers market their own well-established fast 50mm primes, so at first sight this new release may appear puzzling. But Sigma has included a number of features which distinguish this lens from those older designs, including an aspheric element for superior correction of aberrations, an oversized barrel design to reduce vignetting at wide apertures, a rounded diaphragm for attractive background blur, and 'super multi-layer' coating for reduced flare and ghosting. But perhaps of most interest is the ring-type ultrasonic motor for fast and precise autofocus with full-time manual override, here making its debut appearance on a 50mm F1.4 lens. This has the benefit of providing autofocus to owners of Nikon's entry-level D40(x)/D60 bodies for the first time on a 50mm prime; however it unfortunately comes at a cost to users of older Pentax DSLRs, as the effective 'KAF-3' lens mount specification means AF won't work on models which don't support SSM.
The Sigma 50mm F1.4 has arrived to undoubted excitement and anticipation; as the first new, reasonably affordable fast 50mm lens for many years, it has the potential to redefine the quality obtainable in this popular class of lens through the use of modern optical design and manufacturing techniques. But it also currently commands a hefty price premium; the Sigma is considerably more expensive than any of the camera manufacturers' own 50mm F1.4 primes. So the obvious question is whether the optical quality can justify that additional outlay of your hard-earned cash; let's find out.
50mm focal length; fast F1.4 maximum aperture
HSM (ultrasonic type) autofocus with full-time manual override
To be available in Canon, Nikon, Pentax, Sigma, Sony and Four Thirds mounts
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