HD DA 1.4X TC photo

Started Jan 24, 2014 | Discussions thread
Alex Sarbu Veteran Member • Posts: 9,343
Re: But will it AF fine tune the old MF lenses ala the 1.7x?

Britney Elvis wrote:

audiobomber wrote:

Member Pentaxoe just posted a photo of the HD DA 1.4X AW AF Rear Convertor in Pentax Forums SLR Lens forum. The thread is called Teleconverters - again! (Pentax Rear Converter A 2X-S on DA* 200mm f/2.8)) and is not about the new TC, it's about the old A 2X-S.

Quoted from the thread: "Talked to a Pentax source these days. Looks like a (the) "HD DA 1.4x AW AF Rear Converter" is on it's way. It seems to be more than a rumor. He showed me a picture of the new converter. It has the new HD design. I have no further specs or release date though."

This looks a lot like my Tamron 1.4x conv... and it has all the contacts and screw drive, but does not fine AF like the Pentax 1.7 does...
Anyone know if this one will?

That's not what it's supposed to do. It's a "proper" rear converter, with a fixed optical group, which transmits the screw drive shaft or the SDM electric impulses/data so the lens can focus.

So the answer is no. The idea made sense ~3 decades ago, now it doesn't.

What is it about the Pentax 1.7 that allows it to AF fine tune the old MF lenses?

With the 1.7x AF adapter, the optical group in the converter was the one doing the AF. The screw drive shaft was moving the converter's optical group, and was not further transmitted to the lens. It was made when the KAF mount was introduced, to ease transition to autofocus.


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