The Sigma 50-150mm f/2.8 EX DC OS HSM is a fast fixed-aperture telephoto zoom designed for APS-C DSLRs
Sigma’s new 50-150mm is designed for use on an APS-C DSLR, delivering a 35mm focal length equivalent of 75-225mm on a DSLR with a 1.5x crop factor, providing a short to medium telephoto range with a fast maximum aperture of f/2.8.
Designing a zoom of such proportions for comfortable use can be tricky and Sigma’s engineers clearly envisage that this lens will be used with its removable tripod collar attached as this provides a comfortable platform when supporting the lens in the hand. The manual-focusing ring is forward of the collar but is slightly too close for easy reach; the more distant and much broader zoom ring, on the other hand, is perfectly placed and offers just the right amount of resistance.
There is a focused-distance window behind the focusing ring, beneath which sits a pair of sliders to set the focusing mode and to control the Optical Stabilisation system. Both focusing and zooming are fully internal, with no disturbance of the manual-focusing ring and without any extension or rotation of the lens barrel.
Using the lens without its tripod collar means taking a slightly more rearward grip, to maintain balance, and brings the manual-focusing ring to finger-tip touch but makes the zoom ring a shade too far forward for easy reach.
The six SLD (Super Low Dispersion) elements that are used to provide apochromatic correction do a reasonable job but there are traces of colour fringing at both ends of the zoom range. MTF testing at three focal-length settings produced three separate curves: the results at 50mm were very good; at 85mm they were excellent; at 150mm the figures dropped and the lens was a little weak at wide apertures.
Out in the field the size and weight of this lens can become burdensome ‚Äì but no more so than the full-frame 70-200mm equivalent. The padded carrying case is a welcome inclusion that provides excellent protection and a constant home for the lens hood if it is detached from the zoom. Needless to say, the tripod collar is a huge advantage in terms of balancing the lens-and-camera for use on either tripods or monopods.
When treated as the APS-C equivalent of a full-frame 70-200mm f/2.8 lens, the 50-150mm zoom looks very attractive but its maximum aperture is in fact one F-stop behind that of the full-frame version.
The 50-150mm zoom is a useful lens in its own right. It would be nice if it were slightly smaller and lighter as it's noticeably larger than its predecessor. It's actually almost identical in size to the 70-200mm f/2.8 from Sigma, but as it stands it feels robust and durable. The AF system generally performed well but occasionally hunted at 150mm. That, and minor colour fringing, aside this is a very capable and feature-packed lens that is bound to appeal to a lot of APS-C DSLR owners.