After a long wait, Sigma’s new flagship telephoto zoom in its Sport series lens has arrived. Michael Topham had the honour of giving it a workout
Sigma 70-200mm f/2.8 DG OS HSM Sport review: Resolution, shading and curvilinear distortion
The lens delivers a strong set of MTF results from our Image Engineering tests. Centre sharpness improves at all focal lengths by stopping the lens down from its maximum aperture to f/4 and f/5.6. Sharpness holds up well at f/8 and f/11, but does starts to drop off beyond this point. The sweet spot of sharpness across the frame is found around f/5.6, with the solid and dotted red lines indicating central and corner sharpness is superior at wider focal lengths than it is at full telephoto.
There’s a drop in illumination of around 1.4 stops in the corners wide open at 200mm, but this quickly reduces to 0.6 stops by stopping down to f/4. Users will find the fall off is more gradual and less abrupt at 200mm than it is at wider focal lengths. At 70mm, corners are a stop darker than the centre of the image at f/2.8, but this reduces to just 0.5 stops at f/4. This vignetting performance is overall fairly mild as opposed to severe.
As is typical of telephoto zooms, the lens exhibits minor barrel distortion at 70mm, which then turns to pincushion distortion around 100mm. Like the vignetting that’s produced at wide apertures, the level of curvilinear distortion isn’t a major concern about and is unlikely to be an issue for the majority of subjects this lens will be used for. If you’d like to produce distortion-free images, this is easy enough to correct for by shooting in raw and taking advantage of profiled lens corrections.