rehess wrote:
When I switched back to Pentax {from Canon} in 2015, I was surprised to discover that they still supported ‘screw-drive’ auto focus. I purchased two Sigma lenses about that time - a 10-20mm and a 70-300mm - both of them being screw-drive AF, rather than a “KAF3” version that depends on an lens-AF motor, even though the Canon EF-mount version of their 10-20mm lens powered AF by an in-lens motor. I believe Sigma had reverse-engineered the mount, and it had’t been worth-while to rush reverse-engineering the “KAF3” mount. Since then, Pentax has developed a “KAF4” mount - which like Canon’s EF- mount, has motors in the lens for both AF and aperture. In recent years, I don’t believe any company {besides Pentax} has sold a lens for K-mount which auto focuses. I believe if they had released a MILC mount, it would have had been a version of the “KAF4” mount, and Pentax would have been the only company to supply lenses for it. Yes, they could have supplied an adapter for it, but like Nikon, it would have focused with only lenses that had in-lens AF ….. which would have been a real mess. Which is to say, they made the right move of not releasing a MILC with a reduced flange-distance.
When I switched back to Pentax {from Canon} in 201... (
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Yes, Pentax seems strange at times to support the K mount yet update it. I have Pentax brand K-mounts of all flavors. I am not crazy about the KAF4 lenses in that they lack the aperture ring and iris activation lever so they will not stop down on my Pentax film cameras. I have a APS-C Tamron 18-200mm Pentax KAF3 mount lens and a third party 150-500mm Zoom for my Pentax cameras but I think both are older designs and no longer manufactured.