Sigma APO 50-500 mm F4.5-6.3 DG OS HSM zoom
As the proud owner of a Canon 300 mm lens, I’m generally happy with being able to rattle off record shots of birds I see. Often, however, they are mere dots in the middle of a large vista of landscape, and a longer – yet affordable – lens would be an advantage.
Sigma has produced a 10x zoom lens specifically aimed at the sport and wildlife market, and with new optical stabilising technology, the affordable APO 50-500 mm f4.5-6.3 DG OS HSM zoom lens could be just the upgrade needed to open the field to those of us without heirlooms or hedge funds.
It has two modes, one to stabilise images that might suffer from general shake from wind or weight of optics. The second is specifically designed to deal with vertical shake on objects moving horizontal to the lens, such as flying birds, in AI Servo mode. This function is generally unnecessary when using a tripod, of course, and one cannot expect miracles from it when attempting to latch onto fast-moving hirundines and swifts, for instance. It also uses quite a lot of battery power, so should be used judiciously on a long trip, and is unsuitable for some Sony and Pentax models.
Auto focus (AF) was satisfyingly quick to lock on a target, though focus ‘hunting’ resulted in a lot of wavering when trying to lock onto a distant or moving bird. Manual focus was also smooth. Sigma’s built-in Hyper Sonic Motor for “quick and quiet auto focusing” meant that the mechanism seemed almost silent.
To zoom, a broad and ridged rubber grip enables the lens to be quickly extended. For field use, I found the zoom lock to be particularly useful, especially for holding the lens in its short position to avoid contact with brambles, but ready for rapid use when a bird suddenly appeared. Without the lock, the lens crept to its fully extended position swiftly while the camera was hanging down from the strap, but the lock could be quickly released when the camera was needed. When extended, the lens showed the minimum focusing distances and maximum magnification ratios for each focal length clearly along the barrel.
The Special Low Dispersion glass produces very true colours with little aberration, and the lens’s ‘Super Multi-layer’ coating means that the image stays sharp enough even at full extension. At 95 mm in diameter, the lens’ light gathering capability was excellent.
Optional filters and 1.4x and 2x EX DG APO teleconverters are available (giving a 70-700 mm f6.3-8 or a 100-1,000 mm f9-12.6 MF zoom according to size). However, the relatively unusual size of 95 mm makes them incompatible with many other lenses; they are also quite expensive. Its close-up capability was very good, with just a touch of distortion, and there was a small amount of vignetting when approaching full extension.
For practical use, I found that the only drawback was the weight. In truth, however, the camera and lens were no more cumbersome than many other such combinations.
Having the option of 50-500 mm in one lens will always appeal to the active field birder, as it enables quick record shots in many different circumstances, without having to change lenses. There are precious few of these options available, and this is one of the best and most reasonably priced alternatives.