[normhead]

I've been looking for the matched 2x TC Tamron sold specifically to go with my lens, but I'm guessing there probably isn't ore than 10 of those in the whole world. Tamron also said the lens will not work with stacked TCs, something I've confirmed.

So, all I can find is the teleconverter for pentax Bower MC 2x.



Opinions? Recommendations? Alternatives?
Type in Pentax 2x teleconverter on Amazon.ca and that's what you get.
Just thought I'd ask.
This lens is listed as a Bower which is one of the brands used by Samyang. The only review I found claimed it has coatings to reduce purple fringing in older lenses.

[Not a Number]

Other than the one pictured is for Canon EOS mount you know more about it than me

[lithedreamer]

There's a Bower (the one you posted?) and a Sears one on amazon.com. If they'll ship to Canada, they might well be cheaper.

https://www.amazon.com/4-Element-2X-Teleconverter-Pentax/dp/B001D6ZISO/ref=s...+teleconverter

https://www.amazon.com/Sears-Pentax-Auto-Tele-Converter/dp/B004TNWVW4/ref=sr...+teleconverter

[thazooo]

There are the Pentax 2x-s and 2x-L. They are PKA only. The 's' should work. The 'L' protrudes into lens and may not work. If you're looking for auto focus, look for a Sigma

[stevebrot]

I've been looking for the matched 2x TC Tamron sold specifically to go with my lens, but I'm guessing there probably isn't ore than 10 of those in the whole world.

Out of curiosity, which Tamron TC is specified?


Steve

[luftfluss]

I guess you are looking for the Tamron SP 2x AF model. Oy.

From what I've been told in the past, the 7 element 2x TC's are better than the 4 element models. USA Amazon has a 7 element Tamron AF TC, although it's not the model specific to your lens. https://www.amazon.com/Tamron-F-Tele-Converter-7MC-Pentax-ZAF/dp/B0060O9RUE/...+teleconverter

[p38arover]

I guess the Pentax F SMC 1.7 AF converter isn't what you want?

I have one of these I no longer need: 2x Macro Focusing Teleconverter: Vivitar, KAX, Telemore...et al Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

I'm sure I have a Pentax non-auto x2 converter here somewhere.

---

Last edited by p38arover; 02-07-2017 at 01:38 AM.

[clackers]

I guess the Pentax F SMC 1.7 AF converter isn't what you want?

I have one of these I no longer need: 2x Macro Focusing Teleconverter: Vivitar, KAX, Telemore...et al Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

I'm sure I have a Pentax non-auto x2 converter here somewhere.

Norm has one.

[Lowell Goudge]

Norm

What lens exactly are you trying to match the TC to?

Is it MF, AF screw drive , or AF SDM

There are a lot of options out there and I know you already have a wide selection of TC's ?

Your not looking for the adaptall2 TC that goes between the lens and the mount are you?

[beholder3]

Opinions? Recommendations? Alternatives?

I wonder why you'd bother.

From all I have ever used personally (6 different teleconverters on Pentax and 4 different ones on Canon) and what I read from others only the very best x1,4 TCs are worth using them versus simply cropping (unless we talk about very old, obsolete low pixel count cameras maybe even with AA filter).

On Pentax I only see the DA TC as alternative to cropping using a good lens on a modern camera.

And I have not ever seen any raw images proving that any x2 TC on this world across all makers is not worse than a simple crop on a high res camera.

[marcusBMG]

And I have not ever seen any raw images proving that any x2 TC on this world across all makers is not worse than a simple crop on a high res camera.

While I tend to agree with you beholder3, it's not quite the whole story. cooltouch on mflenses did this test with stacked tc's, and demonstrated that the increased magnifiation did demonstrably show improved image information (in the definition of the writing on the sign). But certainly when trying 2x tc's (adaptall 01F, vivitar MC7 macro tc, tamron SP MC7 tc etc ) with a variety of lenses for bird photography I have reached the same conclusion as you. Getting a camera with more MPx is more effective.

[UncleVanya]

I wonder why you'd bother.

From all I have ever used personally (6 different teleconverters on Pentax and 4 different ones on Canon) and what I read from others only the very best x1,4 TCs are worth using them versus simply cropping (unless we talk about very old, obsolete low pixel count cameras maybe even with AA filter).

On Pentax I only see the DA TC as alternative to cropping using a good lens on a modern camera.

And I have not ever seen any raw images proving that any x2 TC on this world across all makers is not worse than a simple crop on a high res camera.

Norm routinely stacks the 1.7x and 1.4x on a DA* 200 and gets results that exceed cropping and exceed some other lens combos. It's easy to degrade images with a poor teleconverter so I understand your point.

---------- Post added 02-07-17 at 09:59 AM ----------

I don't recall which Tamron you have but this may help:

René Purwin , Aug 08, 2008; 06:29 a.m.
I have the 60B too on my Pentax cameras and it is a very good performer evewn on the K20, which is a challenge for old lenses. The weight is a real challenge. When I started using the lens handheld, all images were blurred, even at very short shutter speeds. I never thought, I could blur a shot at 1/4000s, but I did, even with SR. After a couple of weeks practicing, I got better, though. The 300/2.8 may be heavy, but it is really made for fast handheld shots. It woks very well with the Pentax 1.4x-L and 2x-L tele converters, which just fit. (The protruding lens elements of these converters fit very snugly into the lens barrel). With the Adapatall-PKA adaptor usage is very convenient and exposure metering reliable.

Found here: Tamron SP 300mm F2.8 60B & Pentax *istD at lake Zurich - Photo.net Pentax Forum

If this is accurate and matches what you have then the Pentax 2x-L Rear Converter A is perhaps the most available high quality choice.

If you need AF I'm at a loss since I don't know the AF market outside of the 1.7x F and the 1.4x HD DA.

[beholder3]

Well, stacking with really strong multipliers does create the same situations you have with older low res sensors. They simply can not keep up with their pixel count on the details. I would assume on a 100 MPx APSC the crop would clearly outresolve the stacked TCs. So my intention was to comment on single TC usage.

Therefore I still would challenge anyone stating the result of most TCs (except a few very good x1,4s) is better than the crop on say a K-3 sensor.

But obviously there are always exceptions to the "rules".

[luftfluss]

Having used the A 2x-L last year on the very good - but not great - A 400/5.6, here were my takeaways (as a wildlife shooter):

- The quality of the lens has a huge effect on the perceived quality of the TC. Call me Captain Obvious But a fast lens with few optical flaws will definitely utilize a TC to its best advantage. Mediocre lenses will get destroyed by a 2x TC.

- TC's are not intended to bring distant subjects nearer. The TC is best used when the subject is already close enough that you'd take the shot without the TC.

- For all the talk about "IQ loss" with a TC, one aesthetic facet you will always get with a TC is the opportunity for greater subject isolation. If the subject is less sharp, but the background is deliciously creamy, then perhaps there isn't "IQ loss" - its "IQ different", and different in a way that is better.

- In ideal conditions (strong sunlight) the A 400/5.6 + A 2x-L combo produced noticeably more detailed images than the A 400/5.6 by itself. In all other situations, I felt that the degradation of sharpness coupled with the required increase in ISO in order to control camera shake/subject movement produced results that were only slightly better (and more difficult to obtain) than simply cropping my A 400/5.6 image.

- I eventually sold the A 2x-L to fund other purchases. However, despite its limited usefulness on my A400/5.6, I miss it, because it was really good when the stars aligned.

[normhead]

Well, stacking with really strong multipliers does create the same situations you have with older low res sensors. They simply can not keep up with their pixel count on the details. I would assume on a 100 MPx APSC the crop would clearly outresolve the stacked TCs. So my intention was to comment on single TC usage.

Therefore I still would challenge anyone stating the result of most TCs (except a few very good x1,4s) is better than the crop on say a K-3 sensor.

But obviously there are always exceptions to the "rules".

There may be instances where using TCs doesn't provide better results than no TC, because the original lens already resolves all relevant detail without the TC.

But, there is also a point where you back up so much the lens no longer resolves all relevant detail. At that point adding a TC will for a time continues to resolve all relevant detail, until you move back so far you need either stacked TCs or a better lens.

SO while I'm sure there are lots of instances where no improvement is seen with a TC, there are also many instances where a TC improves the image considerably. That's why people buy TCs.

Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

I'm using the Tamron SP AF 300 2.8 LD [Il} which is screw drive, and I'd definitely like to use the AF. And the lens is rated a 10 for sharpness on the forum, easily good enough to benefit from a 2x TC.

I found an original listing somewhere on the Tamron site that said it would not work well with stacked TCs, and it doesn't. So I'm looking to extend my reach past 1.7x. The Tamron site also listed the matched TC that was released with the camera, but months of watching eBay hasn't found me one, so I'm looking to see what else I might use.

When I bought the lens , of course I hadn't read the stacked TC warning. SO I was seriously disappointed when I couldn't get the same results with the 300 I got with stacked TCs with my DA*200 2.8 on the K-3 which gives me 2.4x magnification. So 2x wouldn't even be what i was hoping for. But it would seem to be really hard to come up with even that.

Especially bad since the only current Pentax TC vignettes on the K-1.

The good thing is the 1.7x gives me 510mm ƒ4.5 and is spectacular on the K-3. The focusing rotation on the Tamron is very loose and very short, probably the easiest lens you can buy for use with the 1.7x. One little pinky on the focus ring, it turns to close focus incredibly quickly, and then the 1.7x locks focus, usually immediately.

But I still want the option of 600 5.6 with AF.