Review of the Sigma 70-300mm DG Macro lens
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.
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.