[Lowell Goudge]

i don't think it will be a huge upgrade from 400 to 450 for focal length . the next step will be da560 modern lens , sigma 500 f4/5 , or 600/4 .
i own 150-450 and 560mm . both work super with 1.4 tc . all my shots handhold with or without TC . 150-450 better image quality and faster , but da560 give me the reach and it's fantastic lens . the only downside PF in high contrast areas .

I think the upgrade the OP is looking for is AF.

[nixxo2002]

I think the upgrade the OP is looking for is AF.

in that case 150-450 much faster

[Lowell Goudge]

For the OP, just a simple thing to consider.

I was curious as to the AF capability of the K1 MKII in terms of the limits on maximum aperture. When I started with AF using a PZ1, most kit lenses (zooms at the time) topped out at F5.6 and the recommended maximum aperture for the 1.7x AF converter was F2.8

When I bought my AF converter, I was able to test it out on Other lenses and found it would reliability focus with my Series 1 70-210/3.5. (V1) and with my K300/4 but it would not focus even in bright sunlight on my Vivitar 400/5.6.

Fast forward to about 2012 and it would focus sometimes with my K5 and tamron 200-500/5.6 but only in bright sunlight.

Fast forward again to today, Having spent the last 2 months using the D-FA 150-450/5.6 and 1.4x Tc on my K1. (Maximum aperture of F8) and never missed focus, even in light that required iso25600 I was curious, so I went to the cupboard and tried the AF converter on my old vivitar 400/5.6. It would not only focus in bright sunlight, but also in the shade.

This leaves me with a suggestion for the OP. Keep the A400/5.6, and pick up the 1.7x AF converter. Clearly, this will be light, and the cheapest way to get to +600mm. As he has a K1 MKII he should be able to at least get some experience with a very long lens

[UncleVanya]

For the OP, just a simple thing to consider.

I was curious as to the AF capability of the K1 MKII in terms of the limits on maximum aperture. When I started with AF using a PZ1, most kit lenses (zooms at the time) topped out at F5.6 and the recommended maximum aperture for the 1.7x AF converter was F2.8

When I bought my AF converter, I was able to test it out on Other lenses and found it would reliability focus with my Series 1 70-210/3.5. (V1) and with my K300/4 but it would not focus even in bright sunlight on my Vivitar 400/5.6.

Fast forward to about 2012 and it would focus sometimes with my K5 and tamron 200-500/5.6 but only in bright sunlight.

Fast forward again to today, Having spent the last 2 months using the D-FA 150-450/5.6 and 1.4x Tc on my K1. (Maximum aperture of F8) and never missed focus, even in light that required iso25600 I was curious, so I went to the cupboard and tried the AF converter on my old vivitar 400/5.6. It would not only focus in bright sunlight, but also in the shade.

This leaves me with a suggestion for the OP. Keep the A400/5.6, and pick up the 1.7x AF converter. Clearly, this will be light, and the cheapest way to get to +600mm. As he has a K1 MKII he should be able to at least get some experience with a very long lens

With older bodies (k3mkii) I know a few people struggled to get the 600/5.6 (645 lens) to work reliably with the 1.7afa. The key reminder is also that proper use suggests that handheld may not be easy since the 1.7x will push iso very high. But then again so will the subjects.

[Lowell Goudge]

With older bodies (k3mkii) I know a few people struggled to get the 600/5.6 (645 lens) to work reliably with the 1.7afa. The key reminder is also that proper use suggests that handheld may not be easy since the 1.7x will push iso very high. But then again so will the subjects.

The high iso capabilities of the K1MKII make this less of a concern. I am still waiting for my K3 MKiii to know where this sensor has an iso limit. Although I agree it is pushing it, I have posted shots with the K1 MKII at iso 25600

[UncleVanya]

The high iso capabilities of the K1MKII make this less of a concern. I am still waiting for my K3 MKiii to know where this sensor has an iso limit. Although I agree it is pushing it, I have posted shots with the K1 MKII at iso 25600

That sensor plus the accelerator makes for a potent combo. I push my Sony to 12800 without a lot of fear but typically hit the files with DXO ultimately.

[Henrico]

My 24 Mp KP outresolves my A400. So I doubt if mounting a 1.4TC will give me serious better results than shooting native 400 mm and cropping in post. Does the 150-450 deliver that more sharpness that justifies using an 1.4TC ?

[UncleVanya]

My 24 Mp KP outresolves my A400. So I doubt if mounting a 1.4TC will give me serious better results than shooting native 400 mm and cropping in post. Does the 150-450 deliver that more sharpness that justifies using an 1.4TC ?

Most people seem to think so.

[jslifoaw]

Most people seem to think so.

Agreed. The A400 did not impress me when I evaluated one. On the other hand, the 150-450 is mostly user limited!

I've also had limited luck using the 1.7x AFA with f5.6 or slower lenses. F4 is usually OK but F2.8 is ideal. I don't recall how the 150-450 does with the 1.7x, mostly because you lose AW, DC focusing, and automatic focal length for SR.

The 1.4x HD DA TC has none of those tradeoffs and is much newer - I expect it to be better but can't speak from experience.

[UncleVanya]

Agreed. The A400 did not impress me when I evaluated one. On the other hand, the 150-450 is mostly user limited!

I've also had limited luck using the 1.7x AFA with f5.6 or slower lenses. F4 is usually OK but F2.8 is ideal. I don't recall how the 150-450 does with the 1.7x, mostly because you lose AW, DC focusing, and automatic focal length for SR.

The 1.4x HD DA TC has none of those tradeoffs and is much newer - I expect it to be better but can't speak from experience.

I own both the 1.4x and 1.7x but I don’t have the 150-450. I can attest that both work on my DA* 60-250/4 and FA* 300/4.5 and both are pretty sharp. I think the HD 1.4x is sharper but that’s potentially difficult to be sure.

[luftfluss]

I found the A400 + K-3 II delivered considerably more detail than the A400 + K-5 II.

The A400 + A 1.4x-L delivered more detail than the A400 alone, cropped.

IMO technique is the limiting factor when using the A400.

[mlag]

I've also had limited luck using the 1.7x AFA with f5.6 or slower lenses. F4 is usually OK but F2.8 is ideal. I don't recall how the 150-450 does with the 1.7x, mostly because you lose AW, DC focusing, and automatic focal length for SR.

The 1.4x HD DA TC has none of those tradeoffs and is much newer - I expect it to be better but can't speak from experience.

The 1,7x AFA focus is a nice step forward on a manual lens, but a huge step back from the 150-450 AF: the screw drive of the AFA with its limited focus range is no competitor for the fast focus mechanism of the 150-450....(or any other focus lens), especially if you know the 150-450 works smooth with the 1,4x TC, there is no gain with the 1,7 imho.

Second thing: the 1,7x loses 1,5 stop of light compared to the1 stop of the 1,4x:
on a base lens of f5,6 adding 1,5 stop brings the autofocus sensor even more to the limits, even in nice daylight. Note that some newer bodies might perform slightly better but expect no miracles. Check the low light meter range in the dslr comparison tool, some meter down to -3EV others to 0 EV.

But don’t get me wrong: the 1,7x performs well , check here a recent shootout: 300mm plus Lens Club: discuss your long lenses - Page 2591 - PentaxForums.com

It is just that I don’t perceive the 1,7x as a step up from the 1,4x , it is more OR , depending on lens. On AF lens I prefer the 1,4x (and rather a bit cropping to match the 1,7x), on manual lens the1,7x .

[fs999]

With a HD DA 560mm f5.6 EF AW you don't loose a stop...

[Lowell Goudge]

Agreed. The A400 did not impress me when I evaluated one. On the other hand, the 150-450 is mostly user limited!

I've also had limited luck using the 1.7x AFA with f5.6 or slower lenses. F4 is usually OK but F2.8 is ideal. I don't recall how the 150-450 does with the 1.7x, mostly because you lose AW, DC focusing, and automatic focal length for SR.

The 1.4x HD DA TC has none of those tradeoffs and is much newer - I expect it to be better but can't speak from experience.

Note that the only reason for one to suggest the AFA 1.7x Adaptor, is not to use it with a modern lens, but to use it to gain both reach AND limited AF capability in a MF lens.

I would never consider recommending it on a Lens with internal focusing motor unless as a last resort.

As for speed, however, if you are close focused with a MF lens, the small element size of the focusing elements of an AF adaptor make it very quick.

---------- Post added 11-02-22 at 07:33 AM ----------

The 1,7x AFA focus is a nice step forward on a manual lens, but a huge step back from the 150-450 AF: the screw drive of the AFA with its limited focus range is no competitor for the fast focus mechanism of the 150-450....(or any other focus lens), especially if you know the 150-450 works smooth with the 1,4x TC, there is no gain with the 1,7 imho.

agreed

Second thing: the 1,7x loses 1,5 stop of light compared to the1 stop of the 1,4x:
on a base lens of f5,6 adding 1,5 stop brings the autofocus sensor even more to the limits, even in nice daylight. Note that some newer bodies might perform slightly better but expect no miracles. Check the low light meter range in the dslr comparison tool, some meter down to -3EV others to 0 EV.

as noted in my post, this is largely camera driven, on a K1 MKII a half stop is nothing in terms of difference in ISO rating and grain

But don’t get me wrong: the 1,7x performs well , check here a recent shootout: 300mm plus Lens Club: discuss your long lenses - Page 2591 - PentaxForums.com

It is just that I don’t perceive the 1,7x as a step up from the 1,4x , it is more OR , depending on lens. On AF lens I prefer the 1,4x (and rather a bit cropping to match the 1,7x), on manual lens the1,7x .

Exactly

---------- Post added 11-02-22 at 07:39 AM ----------

I found the A400 + K-3 II delivered considerably more detail than the A400 + K-5 II

The A400 + A 1.4x-L delivered more detail than the A400 alone, cropped.

IMO technique is the limiting factor when using the A400.

The sensor resolution here is the difference but the question really in this comparison is, does the A400+1.4 rear converter on a k5 IIdeliver more detail than the A400 alone on a K3II and does the K5II sensor low light performance outweigh the need to run higher ISO when using the A400 + 1.4x compared to the A400 alone on the K3II

I've found the 1.7x TC to be practically useless for birding with the DA 560, because the long telephoto results in such short depth of field that the AF in the TC only corrects focus within a few inches. The 560 by itself works really well within 25 to 75 yards, more or less, from the bird, but using the TC reduces the light so much that it won't autofocus except in strong sunlight. Not that it doesn't do well at much greater distances (I've tried it at up to fifteen miles) when your subject is much, much larger. By the way, I recommend stuff "refurbished" by the manufacturer. That stuff generally gets much more care and scrutiny than newly-manufactured because it's done one piece at a time. Applies to auto parts, too. A rebuilt alternator is generally better than a new one. Some of us here, may recall my adventures with Pentax/Precision regarding that 560 I've got. I was persistent and got them to make it perfect, so now it's a dam'fine lens. I think it's worth more than a new one from an assembly line. Though, remembering the old adage, "When you buy a new car, the only way you're going to get your money's worth out of it is to drive it."