[crockpotveggies]

Happy owner of the H D FA 150-450mm on a K-1 and the photos are of superb quality. I recently tried the new 1.4x rear converter that isn't officially rated for full frame and had noticeable degradation in sharpness. While I do suspect I received a bad copy of the 1.4, I am tempted to try the old SMC Pentax-F 1.7x SMC Pentax-F 1.7x AF Adapter Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database with the D FA 150-450 to see if there's comparable results.

Anyone try pairing the two? Should I just try another copy of the 1.4?

[Paul the Sunman]

Based on very little evidence, I am hoping for a FF TC from Pentax in this 100th Anniversary Year.

Given that the DFA 150-450 is only f/5.6 at 450mm, I'm not sure I would try to mate it with a TC beyond 1.4x (1 stop). Interested to hear how it works out though.

[Adam]

The 1.7x TC will cover the frame, but note that it's an AF adapter rather than a pass-through teleconverter. This means that there's an element inside the teleconverter that does the focusing. It's adjustment range is limited to the vicinity of the focus setting on the lens, which you may need to set manually due to its long focal length.

[david94903]

I can't speak to the current Pentax 1.4 TC as I've never used it. But I used to own the Pentax 1.7 TC, and when paired with my D-FA 150-450 on my K-3 and my K-1, the results were less than acceptable for me. The 1.7 TC is old tech and it's primary purpose, the purpose that I bought it for, was to add AF to M lenses. It never made a great TC for me. I also had the Tamron 1.4 TC that I paired with my 150-450, the results were better but still underwhelming compared to the the native IQ of the 150-450. Like Paul the Sunman mentions above, I too am hoping for a FF TC from Pentax soon.

[Gopersuel]

Recently I acquired a Bigma OS HSM and I wanted to do some tests with the pentax 1.4 HD TC and with the pentax TC 1.7, the tests were disappointing with both Teleconverters, with the 1.7, you lose the AF capability, you have to pre-focus and then finish blurring with the camera . It is slow, loses two light steps and the image quality is fair.
I do not recommend it.
With TC 1.4 you don't lose the AF, you lose a slight step and bullets noticeably, if you plan to trim later, it can work. But the image quality is better without CT. Add, that the AF is erratic.
In the improvement Pentax 150-450 and the images are more profitable, but I still prefer the quality of the images without the TC.
I thought that my copies of the Teleconverters would be bad, testing up to 300 mm, the quality with TC 1.7 was good and with TC 1.4 were very good. Therefore, it is not a problem of teleconverters, but they do not get along very well with certain objectives.
They should only be used with luminous lenses.
Perhaps a partner has obtained better results, I would appreciate your comment.
regards

[clickclick]

I have both the 1.4x and 1.7x, and would say it's a real toss-up. In general, I get better results with resizing and cropping. If you check out the review here on PF regarding the 1.4 and the 150-450, you'll see that while the 1.4 doesn't take away, it doesn't add much either.

Testing the HD Pentax-DA 1.4x Teleconverter with the D FA 150-450mm on Full Frame Review - Introduction | PentaxForums.com Reviews

[Gopersuel]

Thanks for your comment, I will have to test more calmly.
regards

[Apet-Sure]

It's interesting to me that some combinations of certain TC+lens seem to hit a magic sweet spot of performance. I'm not an optical design engineer, though I was a product design engineer for many years. As I read various articles and threads about using this TC with that lens, there seems to be a wide spectrum of results that aren't necessarily predictable. I recently experienced this myself. I had bought a brand new Pentax K T6-2X TC back in the day when they were in production. Haven't used it much over the years. Average user rating here on the forum is 7.8, so not very impressive. A few months ago I decided to put my Pentax-M 50mm f1.7 lens on it and take a few shots just for the heck of it. (This was my best lens until I recently bought a Pentax-F 100mm f2.8 Macro.) The shots with this combination were amazingly sharp, not at all what I expected. Scratching my head... This converter is designed for lenses in the range from 135mm to 300mm, so why did it work so well with my 50? I now want to try it in combination with the 100mm Macro. Based on my reverse-random chrono-betical analysis algorithm, I think the results might be great or terrible.