[bdery]

I got the 1.7x AF TC ast Monday, a lucky find on the used market.

My longest lens is the 60-250 (modified for full frame, shot on the K-1). There is no real reason to use it with a shorter focal length, so that will be my go-to setup if I'm satisfied.

Here are a few test results (all images are clickable to larger sizes).

Heavily cropped center of the frame



Nice detail in there.

Slight vertical crop to make a better picture, not a particularly exiting subject but shows the bokeh (no damaging effect vs the 60-250 alone) and details:



My favourite shot : the moon. Here is a B&W version:



To get this, I used 10-seconds timer and electronic shutter (that made a huge difference) and shoot RAW. No special processing involved, some sharpening and clarity enhancement, that's all.

Considering that we're under a heat wave, that it was not fully dark, and that I'm still learning the ropes of that TC, I'm quite pleased.

Previously my best moon shot was when I was testing the 150-450, in winter, with the K-3 (more noise so I used a lower ISO value) with a brighter and closer to full moon. The results are not too different:

[gatorguy]

That particular Pentax TC has been great for me with any of my speedier lenses, anything F4 or less shows almost no negative effects (other then light) unless pixel-peeping. It's not nearly as clean with 5.6 and up.

[clickclick]

I've also had good results with that same combination on my K-1 II. The IQ from that pair and that sensor resolution work well together. It doesn't hold up as well on my K-3 II, but it's still quite good.

[bdery]

I've also had good results with that same combination on my K-1 II. The IQ from that pair and that sensor resolution work well together. It doesn't hold up as well on my K-3 II, but it's still quite good.

Surprisingly, my K-3 had trouble exposing properly. I don't know if I did something wrong, but using the same parameters as with the K-1 II, the K-3 did not yield images as bright. Something to investigate.

[jpzk]

Surprisingly, my K-3 had trouble exposing properly. I don't know if I did something wrong, but using the same parameters as with the K-1 II, the K-3 did not yield images as bright. Something to investigate.

This particular TC has been very good with my DA*300/4 (and the K3 !), even better than with the HD 1.4x Pentax one, especially when "birding".
Your pictures are great, BTW.

[luftfluss]

I find that the 1.7x AFA performs appropriately from an optical standpoint - more image degradation than my A 1.4x-L, but a little bit less degradation than my A 2x-L.

The autofocus is persnickety and easily confused - especially when the DOF is very thin, like when coupled with a 300 2/8 and shooting wide open - but with use one learns.

[bdery]

This particular TC has been very good with my DA*300/4 (and the K3 !), even better than with the HD 1.4x Pentax one, especially when "birding".
Your pictures are great, BTW.

Thanks for the compliments.

The surprising thing is that the K-3, when set to manual mode, did not expose similarly to the K-1 II when the same shooting parameters were entered. I will need to explore this.

The autofocus is persnickety and easily confused - especially when the DOF is very thin, like when coupled with a 300 2/8 and shooting wide open - but with use one learns.

Your mouse image is fabulous.

I agree that AF needs to be learned, but I can accept those limitations, and I'll often be close to infinity anyway.

[bdery]

Yesterday's capture (link is clickable for larger view).

Same technique, K-1 II, 10 seconds timer, electronic shutter. Mounted on a sturdy tripod with gimbal head.

Best results with that pair are certainly near infinity. In this case, the pair appears to perform about as well as the 150-450. And I had to work harder to adjust the image shown above from that lens (shot with the K-3, granted).

[normhead]

Another great use for the 1.7 is to increase the magnification of the 100 macro. I was out the other day with that combination, and really enjoyed it.




That gives me 170mm ƒ4.5 (macro). I don't need no stinking 200 macro.

[bdery]

Another great use for the 1.7 is to increase the magnification of the 100 macro. I was out the other day with that combination, and really enjoyed it.

That gives me 170mm ƒ4.5 (macro). I don't need no stinking 200 macro.

I had not thought about that, but indeed it's a fun way to increase effect vie magnification. It seems to preserve the fine details quite well.

Using the TC is full of challenges, in particular stability, but when used well it delivers impressive sharpness.

[bdery]

A thought occurred to me yesterday night.

The K-1 II asks me for the focal length of the system, and I input 450mm, the closest to 470mm offered (that's the value of the 60-250 with 1.7x).

Now, I wonder... if the SR system is trying to stabilize, it's aiming for 450mm. But that's not the real value. So... even though SR is invaluable at longer focal lengths, should I refrain from using it? Maybe it explains why some of my images are a bit soft, while others (see moon shot) are razor sharp?

What is your experience?

[normhead]

It's often an issue, bu I don't think a few mm official length makes a whole lot of different. The above shots were done with the camera set to 180, not 170, My 510mm images are taken at 500mm. My 340s are taken at 350. I've never considered it a problem but it could be that the SR is slightly degraded. But it still works well.

[caliscouser]

The K-1 II asks me for the focal length of the system, and I input 450mm, the closest to 470mm offered (that's the value of the 60-250 with 1.7x).

250 x 1.7 = 425 or do I have a defective calculator?

[bdery]

250 x 1.7 = 425 or do I have a defective calculator?

You are absolutely correct, I do not know what happened in my mind when I wrote 470...

[normhead]

You are absolutely correct, I do not know what happened in my mind when I wrote 470...

It's the login password of his Pentax forum account. Now we can take turns being bdery