Originally posted by THoog There is only ONE way to get third parties to make K-mount lenses, and that is for there to be enough people buying K-mount lenses to make it profitable. For better or worse, Hoya's positioning Pentax as a "budget" brand means that Pentaxians are less likely to spend the big bucks. So not only are there 8+ Canons and 8+ Nikons and 1+ E-mount for every K-mount, the K-mount owners are less likely to pay MSRP for high-priced new glass.
Actually, it isn't so much about the number of cameras sold in a given year as it is about the number of K-mounts in the market altogether (what is referred to as the 'installed base'). While the objective Ricoh had when they introduced color on camera bodies was, of course, to sell them to young Japanese women or as a second K-mount camera in a western household, the
goal has been to dramatically increase the installed base of K-mounts in the wild. Ricoh doesn't care - Tamron doesn't care - Sigma doesn't care - what is wrapped around the K-mount. They only care that more K-mounts exist at the end of this year than did at the end of last year.
The reason is, of course, that third-party lens purchases happen after the camera is already owned. Maybe a 17~70 is a better lens than a kit lens. Maybe a long zoom is better for youth sports. Whatever.
It takes time and money to set up for a run of K-mount lenses. They're more complex because they have to have screwdrive [EDIT: Corrected - mechanical aperture actuator]. Sigma and Tamron won't sell as many as the other mounts - so the set-up expenses and opportunity cost is spread over fewer units. At a point it is apparent the necessary final retail price is prohibitive - you've breached the line of diminishing returns - so they just don't do a K-mount version.
When the installed base of K-mounts gets large enough again they'll make lenses in K-mount.