Originally posted by kunik
I apologize for starting a thread on an issue that has probably been re-hashed over and over but I still find contradicting information around the internet so I'm looking for some help to clarify.
I have the Pentax FA*300mm F/2.8
Which teleconverters WILL work with this and maintain autofocus? And which ones are any good?
Does the Sigma 1.4x even fit on this lens?
Does anyone here have this lens or something similar (DA*300mm) that can share their thoughts. As usual we have the problem with Pentax that I can't just go down to the local store and try things out - I have to order things in (from Japan sometimes) which makes getting things right the first time very important.
While trying to balance the boosted zoom with image quality I'm looking at staying away from the 2x TC's and staying with the 1.4-1.7x range.
To contradict the general consensus I do shoot sports photography professionally with a Pentax setup and I'm not willing to sacrifice much in the way of image quality
Thanks for any help in advance
The Tamron 1.4x AF TC works with the FA*300 f2.8 and f4.5. However I believe it's not available any more. It is generally regarded as the best of the 1.4x TC's if you can find one. I have one that I used with my FA*300 f4.5, I sometimes now use it with my FA50 macro to give me slightly more reach.
The new Kenko 1.5x DG TC also works on the FA* 300 lenses. I've heard that it's pretty decent.
Neither the Tamron or Kenko TC's work properly with the DA* with SDM, the Tamron does allow the SDM to function, but it is hesitant and sometimes fails to lock. Some (all?) of the Kenko 1.5x DG TC's don't seem to have the SDM power contacts in place, so the SDM doesn't work at all.
The Tamron and Kenkos will of course work in manual focus of course.
The Earlier Pentax 1.7x AF TC will also work with your FA*300 f2.8 as it has it's own AF system, you will need to put your FA*300 into the MF setting.
I don't know if the Sigma 1.4x will work with the FA*300's or the DA*300. I do know that it protrudes into the rear of the lens so it may foul the rear elements. I don't know if it has the SDM power contacts either.
If you are using a DA*, I would suggest that you wait for the upcoming SDM rear converter to come out from Pentax.