Pentax 1.4 rear converter comparison
Best regards, John
It's also WR and gives slightly better IQ

. My Flickr
I'd expect the advantage to be image quality as the Pentax converter is designed with such lenses specifically in mind.
Surely the Tamron one is too?? If not what is it designed for?
John K
What I meant was that the Pentax converter is designed by Pentax for its own lenses, making it possible to have a more specific set of design parameters.
Best regards, John
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Best regards, John
I have both (now)
Several Months back I had the same dilemma and wrote on PU that proper testing under strictly controlled conditions confirmed no difference between either in optical performance.
They were so uncannily identical I suspected they were from the same stable.I returned the Pentax and got a refund and quite happily used the Tamron.
However, in the depths of winter I spent some considerable time out on a nearby, very exposed estuary photographing migrant wild fowl and despite performing "optically" very well, the Tamron developed a tangible lack of "tightness" (security) with the 300 DA* mounted on it.
It still performed well optically (see Water Rail below);

Clearly however, I was concerned about potential problems given the very extreme weather conditions I was exposing my equipment too out on the marsh.
I duly "re-purchased" the Pentax HD; This time however I not only found the Pentax HD Converter was very different to the Tamron but very different to the firsts Pentax HD Converter I purchased (directly from Pentax on the release date)
This unit actually seems to improve focus speed when coupled with the 300 DA* and as we know maintains good IQ
So the bottom line: I do think there is a performance improvement, certainly a weather sealing advantage but in IQ terms I honestly can detect a discernible difference but can't help but think there must be and over time it will become apparent, and I am sorry to end on such a nebulous and unscientific final comment.
Daronl
Enjoy life
Many thanks for all of your comments. It was basically what I was thinking. Not a huge difference but probably more comptaible with the Pentax lenses. Not sure that it would communicate any better than the Tamron.
The Tamron doesn't communicate with the camera whatsoever whereas the Pentax does therefore it stands to reason it communicates better.
. My Flickr
Andy
A few bits & Bobs
Well mine is great on a K3 and DA300* need a bit of practice with it especialy for moving subjects but that`s a combination of my inabilities and the AF on the K3 not being up to much.


Enjoy life
cedricd
Member
East Suffolk
Would appreciate any thoughts or observations.
Enjoy life