Sigma 70-300mm f/4-5.6 DG OS - £300/$360
Compared with Sigma's 70-300mm APO lens, the newer Sigma 70-300mm f/4-5.6 DG OS ditches the macro facility but adds a four-stop optical stabiliser. That's great news for Canon and Nikon users and good news for Pentax and Sony photographers as well. We find that optical stabilisation gives better and more consistent results than sensor-shift stabilisation, especially when shooting at long telephoto focal lengths.
In common with the APO lens, the OS model only has a basic electric autofocus motor, instead of Sigma's HSM (HyperSonic Motor) system. Sigma has missed a trick here, since its motor-based HSM usually works well and its ring-type HSM is excellent.
The front element both moves out and rotates during focusing. A focus distance scale is printed on the lens barrel and comes complete with a depth of field indicator marked with f/11 and f/22 calibrations.
Whereas the Sigma APO lens has three SLD (Special Low Dispersion) elements, this OS lens has only one. We'd therefore expect chromatic aberrations to be a problem but, as it turns out, the OS lens performs even better, turning in some of the lowest colour fringing test scores in the group.
There are decent levels of sharpness throughout nearly the whole zoom range, only dropping off noticeably at the 300mm end. For dull-day shots, contrast is pretty good, and much better than with the Sigma APO lens. All in all, it's a much better buy for the money.
Sharpness test
Outright sharpness isn't as good as with Sigma's cheaper APO lens, but in practice optical stabilisation helps produce sharper handheld shots.
Fringing test
Despite only having one SLD element, instead of the APO lens's three, colour fringing is basically a non-issue at any zoom length.
Distortion test
Well controlled throughout the range, but the lens shifts from mild barrel distortion to slight pincushion distortion as focal length extends.
Image test verdict
Sharpness could be better at edges and corners of the frame, especially towards the longest end of the zoom range, but overall image quality is good.
Read the full Sigma 70-300mm f/4-5.6 DG OS review
