[janux]

Having bought a brand new lens DA*300 F4. Worked fine at first but recently having more and more touble locking focus on easy targets. This is especially when I have the 1.4 TC attached but even when only DA*300 is attached.

The SDM focus motor is exchanged but my problem is still there.

The symptom is that the SDM motor is running 3-4 times and then stops and I have to refocus again. It is very annoying. I have tested the lens on four different Camera K7, K5, K5II s and K3.

Is this a bad lens or is it just the way this lens i supposed to behave?

I have a Sigma 150-500 and Pentax 55-300WR and with those two I have never had this behaviour.

Kind regards
Jan Högberg

[Mikesul]

The DA*300 is an excellent lens. It usually performs better than other SDM lenses so you seem to have a bad copy. If it is new you may want to go back to your dealer for an exchange.

[zzeitg]

Are the symptoms same in any light conditions (or more frequent in the "dark")? In my case AF is also more frequently hunting when 1.4x TC is used and the light / contrast conditions are not optimal.

[janux]

Are the symptoms same in any light conditions (or more frequent in the "dark")? In my case AF is also more frequently hunting when 1.4x TC is used and the light / contrast conditions are not optimal.

No, it's not more frequent in dark conditions. In my case it's not the hunting that is the problem, more that it want nail focus. You can hear the motor click 3-5 times than it stops and the focus indicator is flashing in the viewfinder. Then I have to refocus but that very often doesn't help either.

[Venom3300]

My autofocus with the tamron 1.4x, DA* 300 and K5 is nearly useless.... It will constantly over shoot the focus, try to go back and overshoot again and rarely ever nails it. It could be because of the camera body I am using. But I know the lens itself doesn't have a problem when used alone on mine.

[janux]

My autofocus with the tamron 1.4x, DA* 300 and K5 is nearly useless.... It will constantly over shoot the focus, try to go back and overshoot again and rarely ever nails it. It could be because of the camera body I am using. But I know the lens itself doesn't have a problem when used alone on mine.

I have the new Pentax TC 1.4. The converter works fine on both my 55-300WR and Sigma 150-500. No focusing trouble here.
So that obviously means that somethng is wrong with my DA* 300, or?

It's not the hunting between near and far end that is the problem. It almost finds focus but just stops when the SDM have been making some noices/clicks 3-5 times.

[KDAFA]

No, it's not more frequent in dark conditions. In my case it's not the hunting that is the problem, more that it want nail focus. You can hear the motor click 3-5 times than it stops and the focus indicator is flashing in the viewfinder. Then I have to refocus but that very often doesn't help either.

Sorry to say that I experience the same problem on DA*200, with a replaced/repaired SDM Motor. Don't know the cause.

---------- Post added 06-22-15 at 11:38 PM ----------

It's not the hunting between near and far end that is the problem. It almost finds focus but just stops when the SDM have been making some noices/clicks 3-5 times.

As above.

One question: Are you using the lens mostly handheld?

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Last edited by KDAFA; 06-22-2015 at 07:42 AM.

[audiobomber]

It could be either the lens or TC. I've had the same trouble with both. I sent the DA*300 back a couple of years ago for a failed SDM motor, because it was focussing very slowly (i.e. the focus motor was moving the lens elements very slowly). I sent it back for repair last year because focus speed seemed normal, but the camera could not confirm focus and would not let me take the shot (same problem you are having).

This spring, I found the DA*300 was OK on its own, but the camera would not confirm focus when using the HD 1.4X RC. The TC worked fine with my screw drive lenses, but would not lock focus on my two lenses with internal focus motors, the DA*300 and DA 18-135. I sent the TC for repair, and they sent me a new one in exchange.

I still have trouble locking focus with the DA*300 in AF-S mode once in a while, but I'm not convinced they will be able to confirm if I send it back. Most of the time it works normally. The AF motor also squeaks loud enough that photographers beside me have commented on it. I'm waiting until if fails again to send it back for the third time.

You should either send the DA*300 and TC back together, or else determine which is causing the problem and send it back. This should be easy to troubleshoot if you have access to another SDM or DC lens.

[janux]

Sorry to say that I experience the same problem on DA*200, with a replaced/repaired SDM Motor. Don't know the cause.

---------- Post added 06-22-15 at 11:38 PM ----------

As above.

One question: Are you using the lens mostly handheld?

Hi. Yes mostly handheld but also very often with a tripod. Can not see any significant improvement with focus error with the tripod.

[KDAFA]

...The AF motor also squeaks...

Same experience with my DA*200, with replaced/repaired motor.

Frankly I'm disgusted.

To begin with my lens' SDM was "dead on arrival". And this is an expensive, pro-grade DA* lens.

After repair/ replacement, the motor squeaks. I mean, come on, SDM is meant to be silent!!!

And on top of everything else, it has this "focusing hesitation phenomenon" as described by the OP.

Honestly, what standard of engineering is this?

[janux]

Same experience with my DA*200, with replaced/repaired motor.

Frankly I'm disgusted.

To begin with my lens' SDM was "dead on arrival". And this is an expensive, pro-grade DA* lens.

After repair/ replacement, the motor squeaks. I mean, come on, SDM is meant to be silent!!!

And on top of everything else, it has this "focusing hesitation phenomenon" as described by the OP.

Honestly, what standard of engineering is this?

Oh, that doesn't sound good at all. I hope my warranty will be of use. Sounds if it's best to send the lens for repair ingood time before the warranty expires

[seeing well]

My problem is that it fails to focus sporadically.
Will work OK for a full day then the next day will fail. I then go through a whole routine of "turn off- Turn on serveral times, twist the focus ring back and forth , disengage the lens and reconnect. All this in no particular order and then suddenly it works. Some daysit happens more than once.
I spend most of my photo time with wildlife shots and the 300 stays on the K3 99% of the time. The few times I've used other lens it has not happened.
I am reluctant to send it away for repair as there is no guarantee it would screw-up in the shop.