An impressive 10x zoom range for just over £1100, but has Sigma been a little over-ambitious with this superzoom optic?
Sigma APO 50-500mm f/4.5-6.3 EX DG OS HSM Review
With a 10x focal-length range, Sigma’s 50-500mm lens truly deserves to be called a ‘super-zoom’. It has a robust feel and offers excellent handling that is complemented by an efficient two-mode optical stabilisation system and Sigma’s high-speed HSM AF mechanism. But has Sigma been over-ambitious in trying to offer so much in a single lens?
There is no escaping the fact that this is a heavy lens but its mass engenders a sense of confidence in the zoom’s build quality and also provides a very comfortable balance when a mid-weight camera body is mounted at the rear. The zoom’s removable tripod mounting platform has moulded finger-grips on its inner surface and can be rotated to suit both landscape and portrait use.
The zoom ring is furthest forward so, as is frequently the case, it is obstructed by the lens hood when the latter is reversed for storage; it is also a little stiff and is best used with the tripod platform rotated aside to create more space. There is little danger of the zoom extending under its own weight and it is therefore unlikely that the zoom lock switch will see much use.
Focusing is both very quick and quiet. Manual interventions can be applied in AF mode via the centrally-placed focusing ring, behind which is located the AF/MF slider and a three-position OS selector (Off/Mode 1/Mode 2). Optical stabilisation is not just a nice addition but an essential feature in such a lens. When set to its 500mm focal length the barrel is extended by 85mm and becomes hard to steadily handhold.
The only disappointment is a severe drop in MTF performance at the 500mm setting. MTF testing across the rest of the zoom range returned some good results, with f/8 remaining above 0.30 cycles-per-pixel from 50mm out to 370mm but the figure drops to a fairly unacceptable 0.17 cycles-per-pixel at 500mm.
Similarly, but more predictably, small-aperture performance was so weak that at no focal length did apertures from f/22 downwards rise above 0.14 cycles-per-pixel. To be fair, this is much less important but there is a case for saying that the maximum aperture for this lens should have been f/16, given that this would still dim to f/22 at the longest focal lengths.
More positively, this lens can cover both full-frame and APS-C sensors and in the latter context its lens thread can be reduced to 86mm (using the step-down ring provided) to reduce the cost of accessory filters. Sigma has also included a high-quality padded case and shoulder strap.
So has Sigma been over-ambitious? Yes, a little. This would be a much better performer if it were a 50-400mm zoom, especially given that it is compatible with Sigma's 1.4x and 2.0x tele-converters for when extra reach is needed. Similarly, shaving the price below the £1,000 barrier would also make it an even more attractive proposition.