[MrB1]

How about considering viewing size. e.g. Cropping half the image from the K-3's sensor would have the same effect as a 2x converter with none of it's added problems, and still give a 6MP (3000x2000) image which could be displayed as an excellent screen image and 8x10 (or A4) print.

Philip

[PlumCrazy]

FWIW.....I have had very good luck using the Tamron AF 1.4X Pz-AF adapter on several different lenses.....very little image degradation especially with the better lenses.
I've purchased a couple of them used in the $150 ish range.

[stihlmania]

I'm debating getting a teleconverter. I would use it rarely so can't justify spending a lot. I've seen many on Ebay anywhere from tens of dollars to hundreds and from manufacturers I'
ve never heard of. Also what's the difference between teleconverters and extension tubes? Any help or suggestions would be appreciated. I've got a K3 and K5. I would use the converter on my Pentax 55/300 mainly. thanks

Something to consider, almost all tc’s work better with a f2.8 or faster lens. I have the HD 55-300 [non plm] and I do not use any tc’s with it. It takes VERY sharp images [ on my K-3 II ] right up to 270mm. I actually use this lens a lot for my macro insect lens as I can stay back far enough so the critters don’t scatter! Cropping in post gives a better picture with my lens than using any tc’s I have tried. Others have different opinions and possibly a better lens than mine.......With my star lenses the DA1.4 x and the AF 1.7 are a welcome addition, very sharp!

[gatorguy]

I've used the Tamron 1.4TC with my 70-200 2.8 and honestly struggle to see any loss compared to the lens alone. Wonderfully pairing IMO.

I've also frequently used my *200 2.8 with the 1.7 Pentax TC, renders just as well as my *300 F4, and even stacked with the Tammy 1.4TC on occasion which gives me more reach than the *300.

Teleconverters have their value as long as the glass is good.