Originally posted by Kunzite Yes and no.
What I pointed out is that Pentax has no reason to make sure their rear converters works with 3rd-party lenses using - in some cases - reverse engineered protocols. It's always the 3rd-party maker who has to be compatible with the OEM technology, and not the other way around.
Originally posted by JASMAZ77 great! so it looks like the new pentax 1.4x rear teleconverter will NOT be compatible with sigma and tamron lenses.
Originally posted by Kunzite That's not what I wrote, and it's not what people are reporting.
It could be that Sigma reverse engineered, and Tamron implemented Pentax' protocols well enough so that it will work.
If this Teleconverter has super IQ and AF with the DA* 300mm f/4, the DA* 60-250mm f/4, and the D-FA 100mm f/2.8 WR Macro, and is rubbish with every other lens, it will be worth every penny to me! If Ricoh/Pentax has compromised the quality of this Teleconverter with those lenses in order to make it work with lots of other lenses, I will be disappointed.
What I am saying is that we all have our priorities, and Ricoh/Pentax has to choose who to make happy in line with their own business objectives. They want to sell lots of Teleconverters, but they also want to sell lots of the three lenses I've identified above. And lots of K-mount bodies that work well with those top-end K-mount lenses plus the Teleconverter, for all of us nature, wildlife, motor-sport, and airshow photographers.
I have the Sigma 500mm f/4.5 APO EX DG, and of course I want it to work with that too! But I can get (and have) other Teleconverters that work with that lens. It is lower priority for me. (I also have another Sigma lens and a Samyang lens, and those are even lower priority).