[LennyBloke]

Have you tried the Tamron TC with your DA*16-50mm Lenny? I bet there's quite a significant difference. Non-screw-drive lenses I've tried (DA 18-135mm, DA*50-135mm, DA*300) do not auto-focus reliably with my Kenko.

No - I haven't tried it with the DA*16-50 - I've only tried it (and the Pentax 1.4) with primes of 50mm or above and longer zooms, and with all of these I have found the Tamron to be pretty good. I did have a Kenko (or was it Teleplus) 1.5 Pz-AF for a while, and that one was much worse for autofocusing reliably.

The Pentax is better overall but in most situations the Tamron is more than adequate.

I'll try the 2 converters with my DA*60-250 later to see if there's any notable difference, and also the DA*55 - as that is SDM only

[Edgar_in_Indy]

mr cardinal said it worked fine for him on the sigma 500mm 4.5 and the k3

Seems to me you're putting words in his beak.

[jpzk]

Have you tried the Tamron TC with your DA*16-50mm Lenny? I bet there's quite a significant difference. Non-screw-drive lenses I've tried (DA 18-135mm, DA*50-135mm, DA*300) do not auto-focus reliably with my Kenko.

Sorry to barge in.

That is an interesting idea.
I wonder if the Pentax HD 1.4X TC would work well on my lens (DA*16-50) which has been modified to "screw drive" only?
Gotta try that!

[pearsaab]

Seems to me you're putting words in his beak.

[yucatanPentax]

Have you tried the Tamron TC with your DA*16-50mm Lenny? I bet there's quite a significant difference. Non-screw-drive lenses I've tried (DA 18-135mm, DA*50-135mm, DA*300) do not auto-focus reliably with my Kenko.

I can't say how much better or faster the AF is on the Pentax HD 1.4 (because I don't have one), but I have the Kenko 1.5 Pz-AF, and it does focus with the Pentax DA* 60-250mm which is a non-screw drive SDM lens

---------- Post added 11-11-2015 at 03:56 PM ----------

Sorry to barge in.

That is an interesting idea.
I wonder if the Pentax HD 1.4X TC would work well on my lens (DA*16-50) which has been modified to "screw drive" only?
Gotta try that!

I'm curious why one would want to use a teleconverter on a wide-to-normal lens, when native focal lengths are available without the extra weight and glass? I'm not arguing and don't know the answer, that's why I'm asking.

It seems you could just use a DA 70mm, FA 77mm, or 100mm lens and have the length you need. I guess my point is that I see using one when there's little to no longer glass available, especially for under thousands of dollars, so it makes sense on a 300 or a 60-250. But on a 16-50, for the same price as the TC, you can buy a DA 70 Ltd and probably be much better off. Probably, I'm missing something....

[jeffryscott]

So, based on the general consensus here, I opted for the Tamron. I will eventually go for the Pentax for the greater compatibility and weather sealing, but for now, the price difference vs. performance difference favored the Tamron.

[pacerr]

I'm curious why one would want to use a teleconverter on a wide-to-normal lens, when native focal lengths are available without the extra weight and glass?

This is certainly a practical factor. My policy over many years is to only use a TC on the best and LONGEST lens in hand at the time considering the trade-offs with cropping.

It would be a very rare situation that would tempt me to use a TC with a lens shorter than 200mm unless I was carrying an absolutely minimal kit. After all, adding a 1.5-2X extension to a WA or 'normal' lens isn't going to gain much advantage -- except perhaps for a slight increase in stand-off distance for close-up subjects.

[LennyBloke]

Okay - I've now compared the AF capability of the Tamron and the Pentax on both the DA*55 and the DA*60-250.

The Tamron definitely works fine with the DA*55 (SDM only lens)

In good lighting the Pentax has a very slight edge, a couple of times the Tamron had to "hunt" a little before locking focus

In low lighting (living room lit with lightbulbs) the Pentax is far better - the Tamron not only had to "hunt" on several objects, it also failed to focus some of the time. The Pentax was slower than in good lighting, but it did get there

So, if you're only going to be shooting in good lighting the Tamron is still a pretty good bet, but when the light levels start to drop you could experience problems

[pacerr]

In low lighting (living room lit with light bulbs)

No doubt true . . . but why would one want to use a TC on either lens under those conditions? A non-TC solution using more practicable lens choices avoids those presumed AF constraints leaving the choice of TC's to more useful applications for which they're suited/intended.

[LennyBloke]

No doubt true . . . but why would one want to use a TC on either lens under those conditions? A non-TC solution using more practicable lens choices avoids those presumed AF constraints leaving the choice of TC's to more useful applications for which they're suited/intended.

I'm not suggesting that you would want to use a TC under these exact conditions - my point was that in lower light levels (maybe shooting wildlife at dusk?) the Pentax is likely to perform far better than the Tamron

[ScooterMaxi Jim]

I have the Kenko 1.5 SHQ (it really is only 1.4x based on my tests) - and by all reports it is the same as the Tamron. Despite having the contacts for AF, this isn't the best of Tamron TCs. I have the SP 140F in Canon mount. It has larger diameter glass and better coatings - and it performs very well on good lenses (the 200 L in particular). Not to say the Pz-AF (Teleplus/SHQ) is a problem, but it is merely in the "good" range overall. Ron (brandrx) over at DP has done a ton of TC testing. He feels that the Pentax is so good that you lose nearly nothing in IQ stacking two of them on good glass such as the DA*300 - but does not recommend any other stacking.

Not that I'm going to use a TC enough to justify the Pentax due to its price, but it does bring an awful lot more to the table than using alternatives. If you plan to use a TC quite a bit and have the cash, it is pretty clearly a fine choice.

[vonBaloney]

I have the Kenko 1.5 SHQ (it really is only 1.4x based on my tests) - and by all reports it is the same as the Tamron. Despite having the contacts for AF, this isn't the best of Tamron TCs.

There may be more than one version out there of these, but I did a side-by-side comparison of the Kenko 1.5 vs the Tamron 1.4. They are the exact same except possibly for the coatings. The color cast was different between them but nothing else was -- I could tell no difference between the FOV or the level of detail retained. It was an indoor test, so if the coatings are in fact different it is possible one would suffer more in flare-prone lighting, I don't know. And when put on a high-quality telephoto, the ones I've used have been great optically, no complaints at all, but I haven't tried it side-by-side with the Pentax. To me, the non-reporting of the correct adjusted focal length is the big drawback -- if you're on a tripod with SR off it is ok I guess (although still would be nice just for cataloging purposes), but if you're handheld, that's when you need it most. (Although correct reporting is limited to Pentax-branded lenses.)

[clackers]

Sorry to barge in.

That is an interesting idea.
I wonder if the Pentax HD 1.4X TC would work well on my lens (DA*16-50) which has been modified to "screw drive" only?
Gotta try that!

Works fine on my screwdrive modified DA*50-135.

[ScooterMaxi Jim]

There may be more than one version out there of these, but I did a side-by-side comparison of the Kenko 1.5 vs the Tamron 1.4. They are the exact same except possibly for the coatings. The color cast was different between them but nothing else was -- I could tell no difference between the FOV or the level of detail retained. It was an indoor test, so if the coatings are in fact different it is possible one would suffer more in flare-prone lighting, I don't know. And when put on a high-quality telephoto, the ones I've used have been great optically, no complaints at all, but I haven't tried it side-by-side with the Pentax. To me, the non-reporting of the correct adjusted focal length is the big drawback -- if you're on a tripod with SR off it is ok I guess (although still would be nice just for cataloging purposes), but if you're handheld, that's when you need it most. (Although correct reporting is limited to Pentax-branded lenses.)

Good points. I'm sure they could have different coatings. Other physical aspects, such as the barrel, appear to match based on the images.

I want to be clear about the other Tamron TC, the SP 140F that I have in Canon mount. AFAIK, that TC was never made available in Pentax mount. It was priced higher, and designed to compete with the Sigma line. The SP 140F has at least one extra coating - green - not seen on the Kenko, and the glass diameter is quite a bit larger to accommodate wider aperture primes (possibly all the way to f/1.4 rather than the customary f/1.7).