[pykeyuk]

Hi, all i have purchased the 150-450 mm ed dc aw i have noticed that the lens is very sluggish to focus if not at all. For example, if i were to focus a bird of prey at 50 metres the lens would see it and then go out of focus and it does this on most things it's very frustrating as its a very expensive lens. The lens is set a on af full qfs/a see attached photos i would be grateful for any help in this matter thank you pykeyuk

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[Haenzel]

Hi, all i have purchased the 150-450 mm ed dc aw i have noticed that the lens is very sluggish to focus if not at all. For example, if i were to focus a bird of prey at 50 metres the lens would see it and then go out of focus and it does this on most things it's very frustrating as its a very expensive lens. The lens is set a on af full qfs/a see attached photos i would be grateful for any help in this matter thank you pykeyuk

What is your focus area? Start with center point focus only and check the results. My settings are the same and I don't experience the problems you describe....

[Adam]

Once you rule out a mechanical problem per the method above, I'd recommend using multi-point AF to reduce the likelihood of hunting. Also, selecting 6m-infinity rather than the full focus range will help speed things up in case the bird does leave the focus area.

[biz-engineer]

For example, if i were to focus a bird of prey at 50 metres the lens would see it and then go out of focus and it does this on most things it's very frustrating as its a very expensive lens.

If it was my lens, I would test it and note the test conditions and the result of each test. If it is the lens AF that is confirmed to not work, I would return my lens to the seller with my documented tests (notes) explaining what the lens does , why it's not normal and why I want a refund / exchange if the lens doesn't work.

A few things to test, and note the test results or behaviour of the lens:
- I would do a simple test using a fixed test target to focus on, at a distance large enough so not to hit the minimum focus distance
- I would try to focus on the target using center point both thru the OVF and in live view mode, note the results.
- I would try to focus on a smooth surface without detail , such as a white wall, expecting the lens AF motor to perform a loop from infinity to nearest focus distance and back to infinity, to check that the AF motor system is able to cover the full range of focus of the lens
- I would then test if the focus limiter is doing its job. First, with lens focus inside the near focus zone, then with the lens focus limiter inside the far focus zone. I would observe and note the behaviour of the lens for each test.
- I would then test if the focus preset works. I would make the lens memorize a focus distance, then defocus the lens manual and press the focus preset button to see if the lens focus will go to memorized focus location. I would note the behaviour again.


If Autofocus doesn't work as expected it can come from the lens or the camera or both.
- To know if the lens is causing the problem or the camera, I would perform the test with the same lens on a different camera, and perform the same tests with the same camera with a different lens.


Then I would take my notes and go to the seller of the lens and explain the problem.

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Last edited by biz-engineer; 09-06-2022 at 08:28 AM.

[pykeyuk]

at the time i was using my K3 + 1,4 converter 15year using pentax cameras + lenes .software photoshop cc + luminar 4 i also have a K1. firmware on the K3 is ver : 1 .40

[TwoUptons]

I think part of the issue is the teleconverter...
You took the photo at 410mm on the main lens, which is probably f5.6 at that point.
Add the teleconverter, and you have a 574mm f8...
Traditionally, it's that f8 that's going to make AF ugly.

But you were shooting at about 1/125s f8 with 100 speed film (1/160 at f29 @1600), so there should have been enough light...
That's a nice "bright hazy day", so f8 should have been fine...

It won't focus as quickly as it would without the TC, but it should do OK in a situation like that.
Unless your subject is super low contrast or something.

Does it focus OK in live view?
I have heard of the AF sensors getting messed with by foreign objects on the mirror...

-Eric

[Sakura]

Focussing with an added teleconverter is indeed a lot slower and less accurate, even with my K1-II

[mlag]

On my k3II the pentax convertor 1,4x and the 150-450 work very well in daylight. You might test auto focus by changing between near and far buildings as subject, that should work immediately.
Birds can be trickier if you shoot through branches or similar difficulties...
For birds in flight the background can distract the autofocus if your tracking is bit off subject sporadically. I prefer center or extended center focus area, but not full screen focus area, especially if background are nearby trees or so. (A clear sky might be easier)... trick is to keep focus on bird in center and only go slightly off center in your tracking of the bird. But at 450 mm x1,4 tc x 1,5 aps-c crop you are shooting with a very long focal length of 945 mm and need a very steady tracking hand!
Note that a comparison with a K1 on this lens combo gives 50% difference in focal length, tracking would indeed be easier...

The responsiveness of the focus can also be tuned with ”hold aufocus status” setting: sometimes slower re-focusing (medium setting) during af.c tracking is better to keep tracking the bird because it reacts less quick to an accidental misfocus. After all its a heavy , long lens combo to track birds in flight, ...