Sigma currently is discontinuing some of its lenses, and seems to be targeting K-mount as the first mount to do so. It was always clear that Sigma would update its long zoom range to its new Sports line, which, if nothing else, is distinguished by granting access to Sigma’s Mount Conversion Service, which gives users the option to keep the lenses they buy when they change to a different supported camera system. The idea is that you could buy a Canon lens and take it with you when you move to Pentax, Sony, Nikon, or Sigma, at a fee and a few weeks’ waiting time (during which, if you were a professional, you could rent a replacement lens from somewhere, or buy for the interim and sell the worse copy when your first one gets back from Sigma).
So far, Sigma has updated or released a number of lenses for its Art line, which is also eligible for the programme, but not much was heard for Sports or Contemporary, its remaining two categories (Sports is for long lenses, Art for high quality lenses from moderate wide to portrait focal lengths, and Contemporary is presumably for everything else).
So when it comes to Pentax mount, people see that the K-mount bodies are selling like hotcakes, at least in some regions, but feet still get chilly whenever there’s a possibility that fewer lenses will be available in the near future. As a result of discontinuations, people then overpurchase lenses that they think they might need in the future, such that remaining stock can disappear quickly. This apparently happened with the 70-200mm f/2.8, 100-300mm EX, and 120-400mm lenses. In addition, some people called their Sigma representatives and were told different things. One speculation apparently was that the 70-200 was discontinued because only two to three of them were sold, per month, for K-mount in the US. Another person was able to place a “back-order” for one, suggesting it isn’t really discontinued.
Sigma have, in a recent interview, stated that supporting Pentax is more difficult than other brands because Pentax still controls aperture through a mechanical lever. This increases research and development as well as machining costs. In spite of this, Sigma have in the past kept the same price point for lenses in various mounts. From Pentax/Ricoh’s point of view, this circumstance may be seen as a competitive advantage, since at least historically, camera makers have sought to sell their own lenses rather than allowing third party lenses to be bought. On the other hand, having a smaller lens collection available for purchase may cut off sales entirely if people take it as a reason to stop buying into bodies.
It’s also true to say that the contact point between the camera’s and the lens’ aperture mechanisms is an additional source of “shutter” noise when shooting at less than widest aperture. Lenses on any TTL system – Olympus, Sony, Canon or other – ultimately need to move their aperture blades into position. (Btw, that’s one reason why cameras with an optical or hybrid viewfinder, such as the Leica M series or Fujifilm X100, are better at street photography.) However, its clear that Pentax’ additional aperture lever is a source of significant noise.
Not knowing what else may happen at Photokina, and whether something special is happening at either Pentax or Sigma to create these perturbations in Sigma’s lens supply chain, I would still like to ask the question why Pentax doesn’t include an additional aperture-control electrical contact on its next generation of bodies to allow third party lenses to be more easily made or mount-converted, leading to a larger available lens selection that could benefit the wider adoption of a set of bodies that for many applications are still the best available.