Shadowblade wrote in post #17632421
Besides, A-mount is a dying format. E-mount is a rapidly-growing one - and, unlike Canon and Nikon (where shooters often already have an established stable of lenses with a low turnover rate, due to the mounts having been around for a long time), E-mount users are often buying more gear and getting their stable of full-frame E-mount lenses set up.
It's all a matter of timing, and whatever the sense of the direction the market is moving at the time the decision to build an e-mount vs and a-mount was made. It's easy in hindsight to say that 2 years ago when the a7 cameras hit the market that Sigma should have invested more resources in developing FE lenses, but there was a lot of uncertainty about how well consumers would adopt the a7 system. At the time, someone at Sigma likely decided that the a-mount was a better use of resources at the time.
Even if Sigma was confident about the adoption of a7 cameras, they may not question "if" they should enter the market, but they will have to question "when" to enter the market. Do they do so prematurely when there are fewer potential consumers for FE lenses, or put their resources elsewhere until the market matures? It's a risky proposition when their ability to sell FE lenses is directly tied to how well Sony can sell the bodies.
Shadowblade wrote in post #17632356
There's no risk involved in adding an E-mount option to existing Sigma lenses. All it involves is a spacer and a bit of wiring - just like all the other mounts. Nikon has the longest flange distance, so it has the shortest spacer. Canon has a longer one. Sony E-mount would require a longer spacer still.
Without insight in Sigma's production processes its impossible to know for sure, but given that the mount is built into the lens body, there likely is some point at the latter end of production where a decision is made about how much production capability is allocated to slapping an EF mount in front of a lens, and how much is allocated to slapping an A mount or potentially an FE mount. Production capability at any point of the process is finite, and the tolerances should be very tight end-to-end. If they stock out of EF lenses because of a bottleneck at the "mount attachment phase", they're literally leaving money on the table. Sigma as is, struggles for months to keep up with the demand of their new lenses upon release.
This is where the tires of marketing meet the road of business operations. I can see why Sigma had the stance they did when the a7 cameras initially hit the market, and why their position has very recently changed as the market for a7 cameras is starting to mature.