[tuggie76]

I have a K3ii and a 300 mm Pentax lens. I sometimes need a tad extra reach, would I be best pleased with the 1.4 or 1.7 convertors? And are any other brands acceptble?

Thanks.

Tuggie76

[pearsaab]

here are the links to the different teleconverters and you can read up on the good, bad etc


the first 2 you will need to find. the last one you can buy but pricey. I have all 3 and could answered questions if you still have any after reading reviews




https://www.pentaxforums.com/lensreviews/Pentax-Rear-Teleconverter-F-1.7x-Autofocus-Adapter.html





https://www.pentaxforums.com/userreviews/a-tamron-f-1-4x-pz-af-mc4.html





https://www.pentaxforums.com/lensreviews/da-teleconverters-c70.html

[amodali]

crop... and be happy

[david94903]

I've owned both the Pentax 1.7 TC and the Tamron 1.4 TC. I'd purchased the 1.7 in the late 80's so I could turn all my M lenses into autofocus lenses on my PZ-1. The 1.7 is a bit on an odd duck. It is a TC but it's other true function is to allow M lenses to function as AF lenses. I think it was bit of a short lived experiment. Using an M50 lens with the 1.7, the image quality was good, and the magnification was a nice bonus. In the early 90's I bought the Tamron 1.4 when I bought my F-300 F4 lens. The 1.4 was a lot easier to use than the 1.7, especially hand held, and was just a straight TC, no "other" function to impede it's true nature. When I went digital, I found the 1.4 to be more useful than the 1.7. I sold the 1.7 since I wasn't using it and kept the 1.4. Later, when I upgraded from the K-3 to the K-1, the 1.4 didn't seem as sharp, especially with the D-FA 15-450. It may be that the increased focal length and the high megapixel sensor showed more flaws of the old tech and my own shooting style. I ended up selling the 1.4 too, waiting for a modern full frame TC to come along.

Since you're shooting on a APS-C sensor with a 300mm lens, I'd recommend the 1.4 over the 1,7, You'll have minimal IQ loss per my personal experience.

[Pentax Syntax]

I have both the 1.7 and the 1.4 (2X Tamron also). Be aware that the Tamron teleconverters transmit the focal length to the K-3ii body directly without the 1.4 X or 2X conversion (ie 300mm instead of 420mm). On the other hand, the Pentax 1.7 will transmit the calculated focal length equivalent (320). To get the Tamron s to NOT transfer that information you have to tape over some contacts. If you are on a tripod and not using IBIS it’s no big deal but the Tamrons are a pain if you use IBIS. You can’t enter the right focal length manually unless you tape the contacts. I like the 1.7 for IBIS and use the Tamrons only on a tripod.

[tuggie76]

Thanks for all the advice so far, I've just found out there is a Sigma 1.4 & 2x. Any comments on these?

[normhead]

Thanks for all the advice so far, I've just found out there is a Sigma 1.4 & 2x. Any comments on these?

Especially with the Sigma TCs there can be problems with them mounting on some lenses. You need to be sure you can use them. Also some lenses can damage even the Pentax TCs, my old Sigma 70-300 being one of them.

I use the HD DA 1.4 most, and the F 1.7x AF adapter occasionally. AF is a wonderful thing.
When looking for small birds my 300 and 1.7 is used most of the time, For larger birds or closer small birds I use the 1.4

On a 300 ƒ4 both will give you increased resolution on the subject. I have no experience with older TCs. I doubt any of them meet the design specs of the HD DA 1.4 TC, which is 400% in crease in magnification and 3% loss of resolution. SO possibly a 37% gain in subject resolution under perfect circumstances. I don't know the design spec of the 1.7 but it also is quite good, as long as the lenses you mount them on are exceptional lenses.

People who use cheap TCs on poor lenses get bad results. To be 100% effective the The lens has to out resolve the sensor by 40% for the 1.4 and 70% for the 1.7x, but that isn't a problem for DA* , FA *, F* or A* lenses. IN fact the 1.7x was designed for A* 2.8 or faster lenses. You didn't mention what 300 you have, so, I can't give you a definitive finalworkd. But my personal preference is to not use the 1.7 on slower than ƒ2.8 lenses. And the 1.7 doesn't let the camera record the focal length. This is important for SR which will have to be input manually. That makes it impractical to use with zooms unless you just set it to one focal length and leave it there. Or change focal length every time you zoom in or out.

With the 1.4 it's all automatic. AF and the camera computes the focal length for SR.

Also, the partial AF on the 1.7 may need to be adjusted in the middle of a burst. It's really not practical for fast moving targets that are covering distance, where as it works fine for small birds hopping around on the forest floor. They generally stay inside the short range of the TC and it acts as a focus limiter, making AF really quick, within that limitation.

[pearsaab]

Thanks for all the advice so far, I've just found out there is a Sigma 1.4 & 2x. Any comments on these?

Was never happy with sigma. 2x from any brand is really disappointing

[david94903]

No experience with the Sigma. I do have a 2x Kiron, fully manual, no contacts, for use on a tripod only. Very sharp but takes a lot of patience. Pearsaab is right, most 2x TC's are disappointing, mostly because the require a lot of care and fussing to use.

[normhead]

People really need to start posting the lenses they've used the TC on when they post. TCs are matched or not to the lenses they use. Advice for one set may not be applicable to to others.

I have stacked the 1.4 and 1.7 with the DA*200 with great results. That's 2.4x. In the Tamrorn notes it says there is a matched TC for the Tamron SP AF 300 2.8 LD [IF] says it will not work with stack TCs, but there is a matched TC that the web says is quite good. I've never seen one in Pentax mount let alone own one.

For the advice in this thread to be worth 2 cents, people who have had success need to be posting successful combinations.
For those who haven't, the fact you haven't doesn't mean others can't pull it off. It just means you didn't.

DA*20 and stacked TCs slideshow.

TCs or Stacked TCs don't work.
You must believe I faked these images.
They work in some circumstances, or people wouldn't still be buying them/

I know several advanced amateur or semi-pro shooters who shoot mainly with the Canon 70-200 and 2x TC. I see them quite frequently. It's odd something so universally used has so many people who claim they don't work. Lat year I meta guy with a Nikon 600 ƒ4, with a 1.4 on it. If you ask any of these people TC doesn't work, can I film their reaction? I'm getting tired of repeating this.







The good thing about the two TCs I have Pentax HD DA 1.4 and 1.7 is they'll work on almost any long Pentax glass. All you have to worry about is the ls smaller Aperture in low light.

The DA*300 with the 1.4 TC is better than the Sigma 120-400, and my A-400. Try it for yourself, if you don't believe me. But please quit posting this TCs don't work nonsense. People don't pay the money we pay for good TCs because they would be better off just enlarging the images.

Using enlarging instead of a TC is the same as using digital zoom instead of optical zoom.
People against TCs should maybe share what mistake they made that led to forming that opinion.

Used a cheap TC or a cheap lens.
Didn't know how to change technique to use the longer focal length.
Bought a TC that didn't work well with the lens it was purchased for.

It's not enough to say it doesn't work, we need to now why it didn't work. And there are so many people out there making it work, "it doesn't work" isn't really a provable answer. (Which is why I've never seen a proof of their notion.) It doesn't matter how many people say TCs don't work, one guy who can make one combo work makes them all irrelevant.

[kkoether]

I recently acquired a Pentax 1.4x HD teleconverter to use on my DA* 60-250mm. It took some getting use to but I'm happy with the results.

[tuggie76]

Thanks for all the help guys, it looks like the Pentax 1.4 for me.

[SSGGeezer]

Thanks for all the help guys, it looks like the Pentax 1.4 for me.

Good call!