[jslifoaw]

Hi everyone,
I took out my 60-250 for the first time in a while. I was surprised and worried to note that on my K-01, the AF was extremely slow when set past 135mm (literally 10+ seconds to focus from one end of the range to the other). It seemed fine at 135mm and lower, where it might be at most a couple of seconds.

On my K-1 II, it exhibited the exact same behaviour in live view, but using the OVF the AF was about as fast as I would expect for SDM at any focal length.

Can anybody with that lens and a live view camera confirm if that's the behaviour you're seeing or if I could be in trouble?

Edit: for clarity I've owned the lens for almost 3 years and can't remember the live view phenomenon since I mostly used the OVF and hardly mounted it on the K-01. The DA55 and DA50-135 don't behave this way either.

Thanks!

[pid]

The af Speed of the 60-250 is not very fast. But if the AF comes from the min. focus it is faster than from max. focus side.

[UncleVanya]

My history with sdm lenses is extensive. Failing sdm can do weird things. If you could post more details maybe I could try my lens and others could too, and we could compile the times but we would need some standard testing to make it meaningful.

[jslifoaw]

My history with sdm lenses is extensive. Failing sdm can do weird things. If you could post more details maybe I could try my lens and others could too, and we could compile the times but we would need some standard testing to make it meaningful.

Thanks for the offer. Before going into details, the behaviour was so vastly different by focal length that I don't think you need to be very scientific:

1) focus on a distant near infinity object (I live downtown in a large city, so I just pointed to another building in the distance)
2) focus on a nearby object (e.g. my balcony or something inside)
3) focus on a distant object again
4) focus on nearby object again

I performed this on my K-01 (live view only), in good daytime light in single (not continuous) AF (multi point) at 60, 85, 135, 200, and 250mm. At 60/85/135mm, the times were pretty constant and pretty short. At 200/250mm, the time is at least 2-3x as long, and the way the lens focuses seems different. You can see the focusing slowly gliding towards the right distance (the SDM makes a steady very quiet whine), while at shorter focal lengths it tends to "snap" a few times to quickly converge to the right distance (the SDM makes a series of quiet squeaks).

The lens ultimately manages to lock focus. The slowness is most obvious when the lens hunts, which might be more likely at longer focal lengths. For small changes in focus, 200/250mm seem to behave no different than 60/85/135mm.

If a video helps, let me know, but the difference was not subtle at all.

I then did the same thing on my K-1 II in live view, and the behaviour was almost identical.

I then switched to OVF (phase detect AF), and there was hardly any variability in AF time at various focal lengths; the SDM behaves by "snapping" to the right focus with progressively smaller corrections (series of quiet squeaks). So the slowness is unique to longer focal lengths using contrast detect (live view) and most noticeable when the distance changes a lot (e.g. hunting / MFD-infinity / infinity-MFD)

The other SDM lenses I have are the DA*55, DA*50-135, and DA*300. The prime lenses seem to behave fine, but obviously don't zoom. The 50-135 does not slow down much on the long end.

I would summarize the "problem" as very slow hunting at 200/250mm in live view only. So maybe it's just by design and I never noticed it before.

[Apet-Sure]

I just ran a series of tests with my 60-250 mounted on my KP. Targets were a brick wall about 250-300 feet away and a plant 6 feet away. I just happened to have the lens set at f6.7 at first. It is cloudy/gloomy today. I pointed at the wall first, physically set the lens at MFD each time, and counted '1 Mississippi, 2 Mississippi' after pressing back-button focus in Live View. Each test run twice.

f6.7 - wall
60mm - 1.5-2 sec
85mm - 1.5-2 sec
135mm - 1.5-2 sec
200mm - 5 sec (with hunting)
250mm - 5 sec (with hunting)

Then I pointed the camera at the plant, set the lens at infinity each time, and repeated the test.

f6.7 - plant
60mm - 1.5-2 sec
85mm - 1.5-2 sec
135mm - 1.5-2 sec
200mm - 2 sec
250mm - 2 sec

I then set the aperture wide open and repeated the two series.

f4 - wall
60mm - 1-1.5 sec
85mm - 1-1.5 sec
135mm - 1-1.5 sec
200mm - 1.5-2 sec
250mm - 1.5-2 sec

f4 - plant
60mm - 1 sec
85mm - 1 sec
135mm - 1 sec
200mm - 1-1.5 sec
250mm - 1-1.5 sec