Sigma makes a lot of lenses in a lot of mounts, but one in particular seems repetitively dramatic. Its 200-500mm zoom range is certainly dramatic-only a 2.5x ratio, but one of the few to reach 500mm. Its f/2.8 aperture is dramatic too, being a constant aperture-the lens doesn't become slower as it zooms-in-and a 500mm f/2.8 lens is quite a rare item. The final dramatic number associated with the lens is its price, which is around $24,000.
We don't suppose Joe 'n Jane Foto will be buying many of these, but Sigma's Tom Sobey tells us that it finds gainful employment in government and similar agencies where a fast super-tele lens is required. "I can't think of any 500mm lenses with an f/2.8 aperture," Sobey tells us, "even non-zooms," f/5.6 being a more typical maximum aperture for lenses this long. So if you really need a fast telezoom, and if you have 24 grand to spend, you're good to go, thanks to Sigma. But there's a catch.
The Sigma 200-500mm lens comes in only two mounts besides the Sigma mount itself: Canon and Nikon. So if you want to use it, you have to use a Canon or Nikon camera.
Other Sigma lenses come in Pentax, Sony (Minolta), and FourThirds mounts as well, so the field evens-out for lenses with somewhat less dramatic numbers than the 200-500mm f/2.8 zoom.
Still, there's a principle at work in the case of that lens which once was the bedrock of SLR marketing: People buy an interchangeable-lens camera so they can use lenses interchangeably, or so the thinking went. If your customers include people who absolutely must have a 200-500mm range at f/2.8, they absolutely must have a Canon, Nikon, or Sigma camera as well. Because they're the only ones the lens will fit.
The bedrock principle at work is that it's the lens that sells the camera body, not the other way around.
TIT FOR WHOM?
By the same token, the lens blocks the sale of a competing camera. There are plenty of reasons why someone might want to use a 200-500mm f/2.8 zoom on a Pentax or Olympus DSLR, not the least of which could be the image-stabilization systems built into models in both lines.
Anyone who needs a 500mm f/2.8 lens is already working in lower levels of light, and there's nothing to say that image-stabilization wouldn't be welcome. But the lens as Sigma makes it is without the company's own OS stabilization technology, and no Canon, Nikon, or Sigma DSLR bodies currently have image-stabilization built-in. So if you have to handhold at 500mm and 1/20-sec., don't drink too much coffee before you go out.
A company making a lens that will sell for more than most people's cars naturally hopes to cast the widest net, and Canon and Nikon still have those numbers. We all understand why Sigma would choose the mounts it did, but in the process they show how the tail and the dog are sometimes interchangeable in the photo trade.
Of course, if you look over the full list of Sigma lenses, you'll find what you do when you look at the full list of most manufacturers' lenses: an argument against interchanging lenses on an interchangeable-lens camera. This argument takes the persuasive form of superhigh-ratio zooms -we've called 'em Stratozooms in the past-that in one unit cover most of the focal lengths ordinarily requiring two or three different lenses.
Sigma's own product of this style includes a 50-500mm f/4-6.3, which is a 10x range, and 18-200mm f/3.5-6.3 (in both standard and OS versions), which is a smidge over 11x. Our experiences with Tamron's chart-topper, their 18-250mm f/3.5-6.3, persuades us that having a smidge under 14x at your disposal can leave you ready for anything. Except, maybe, additional lenses.
The same thought is prompted by Olympus, with a 10x zoom (18-180mm, 36-360mm "equivalent"), and by Sony with an 11+x zoom (18-200mm), and by Pentax with an almost-14x zoom (18-250mm), and by Canon with an 11x (28-300mm), and by Nikon (ditto) in DX format.
It looks like everybody who makes interchangeable-lens cameras, as well as everybody who makes interchangeable lenses, markets at least one lens that asks the question, what does Joe Foto need any other lenses for?
Joe himself could probably come up with a number of answers, and of course probably would if you helped him along.
WHAT IS ORDINARY?
Having a lens that can frame almost everything is a heady experience, but it makes those things it can't frame a bigger disappointment. What, something's got the best of you? Well sure, it happens, even with a 10x or a 14x zoom. If you notice their apertures, for example, you'll see maximums around f/3.5, diminishing to f/5.6 or f/6.3 as the lens zooms-in.
With all the progress made lately in noise-reduction, a lot of thinking seems to hold we don't really need fast apertures-which tend to be expensive-because we can boost the light-sensitivity and reduce the consequent noise pretty well now, at very little cost. It's an acceptable trade-off for a good part of the market, but lower ISO equivalencies still make better-looking pictures. Faster lenses remain a pursuit of customers who buy into high-quality output.