Sigma’s 70-300mm has an impressive list of features but it also calls forth the warning that if something sounds too good to be true, then maybe that’s exactly what it is. Its 70-300mm focal-length range may be more than many users will really need in an everyday tele-zoom but there is nothing wrong with having a little bit of extra power – provided, that is, nothing more essential has to be sacrificed along the way.

The wide zoom ring has a very comfortable feel but its quarter-circle throw is quite highly geared and the lens extends by more than 50mm. Coupled with a close-to-camera hold on the lens, the considerable extension increases the risk of camera shake. It is not possible to steady the lens with a further-forward grip because the entire front section of the lens rotates during focusing – and the instruction book specifically warns against obstructing this movement. Using the lens at its 300mm setting is therefore very difficult indeed. All of this is a huge shame because the 70 -300mm has an image circle big enough to accommodate full-frame sensors and the lens even includes an infrared focusing mark for those who need it. There is also a very useful ‘macro’ capability that, while not being fully deserving of the term, manages a very creditable 1:2 reproduction ratio.

Image Quality
Unfortunately, MTF testing reveals that the 70-300mm is lacklustre at best, climbing above the critical 0.25 cycles-per-pixel value only between about f/8 and f/22 for short-to-medium focal length settings. It fails to get anywhere near the magic figure at any point when set to 300mm.