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.
The trouble with this lens is that it tries to do too much: it's very versatile but it doesn't shine in any department. It offers so much that it cannot possibly meet all of its promises at such a low price-point. Its resolution figures start low and never climb as high as other comparable lenses either and its crucial 300mm performance is particularly poor. The lens is also hard to handle given its considerable extension and the fact that its barrel rotates during focusing.