My K10D sometimes refuses to focus

[mggm59]

I have had this problem several times in the field, but I cannot reproduce it at home.

 

Sometimes, particularly in low contrast situations and with the 12-24DA and 28-80 f2.8 FA lenses, the

camera refuses to focus. It does not hunt, as it happens sometimes, but just emits a faint noise as if the

focus motor tried to spin up but could not move, and there is no focusing action.

 

I have then to switch autofocus off, and the bad thing is that sometimes I then forget to engage autofocus

again after the shot and I happily go on with wrong focus. My fault, because with bad eyesight and too

much auto-habits, I no longer always check the shooting parameters as I once did.

 

Did anybody have similar problems? Is there any solution/workaround? Should I send the camera back

before it goes out of warranty?

 

Thanks

 

Maurizio

[personalphotos]

I've noticed this myself with a Sigma 70-200 on the K10D. I haven't tried it on the *istD yet to test and see if it happens on that body. My solution is to quickly zoom the lens back 20-30mm, refocus and then recompose the shot. It only seems to happen when the lens is at a full 200mm. I haven't noticed this on any other lens now or before including the Sigma 50-500mm. I'm assuming it's a glitch with my 70-200mm which may go to Sigma for checking.

 

I'm surprised to hear you see this on 2 lenses. Does it happen at any particular focal lengths?

[rose_duclos]

Maurizio, I had this same problem when I first began. There is a little knob on the back surrounding the 'ok' button. It should point to the single white box with the dot in the center. This will tell the camera that you want it to focus on the spot in the middle of the focus screen.

[mggm59]

Thanks

 

It seems to happen mostly at wide settings with both lenses (so it seems strange you have

the problem on a tele lens), but I do not remember exactly. As I said, I tried to reproduce

this at home without success. As for measurement point I think it was at center already,

but I am not sure.

 

So, does it mean it is not a bug, it is a feature? No good in sending it back to service?

Nobody tried? It is a bit strange, what could be the cause of such a behaviour?

 

Thanks

Maurizio

[rose_duclos]

Maurizio - check your camera first - to make sure that it's set to center. If it is - then what you're experiencing isn't what I'm describing - and, could be some other issue. I don't use zoom lenses but there are plenty of others here who do - that may be able to tell you if it's an issue with the lens. Do you have a basic prime? If you test a prime and see if the focus is a question - then you can attribute whether it's coming fromt he camera or the lenses... yes?

[cory_zerkee]

I have the same problem with my K10D and Tokina 80-400mm. The Camera's IR focusing needs a decent amount of contrast difference to focus properly. If you are focusing in low light on objects of low contrast, it will hunt.

[mggm59]

Thanks Cory, but hunting is not the problem here. I have it from time to time, and I know

what it is. This is worst to me. The motor makes a brief noise, as if it were trying to move

but it can't, and it stops immediately.

 

Rose, I'll try as soon as it happens again, the problem is that I cannot make it happen at

will, so I cannot experiment. I have several primes, from 15 to 300, but most aren't

autofocus, so... the 300 f4.5 is the only AF prime I have, I'll try with that, but as I said it

seems to happen with wide angles.

 

Maurizio

[raybrizzi]

Yes, it has a tough time focusing at infinity without clouds, a real pain with sunsets. I find the weirdest thing is that if you have the flash on and it can't focus, it discharges the flash with a weird sound and the flash flickering very quickly. Not sure WHAT the possible benefit of that might be other than wearing out the batteries for no reason.

[andrew_ng7]

I've noticed it on occasion to. Most times it's in low light, low contrast situations. You press the AF button or the shutter halfway and nothing. A few times I've fully pressed the shutter and it acts dead. Won't take the picture.

 

I also got a cheap gray card, from a photo magazine, and the K10D refuses to focus on it.

[alex_m.1]

@Andrew Ng:

 

Excuse me, I probably misunderstood something, but how is the AF

expected to work against a gray card which, by its very nature, has

no contrast? Isn't one supposed to switch to MF while setting

exposure and WB with a gray card?

[personalphotos]

You got it Alex. The camera can't focus on 1 solid colour of any kind in most instances. Turn it to manual then do the WB.

[andrew_ng7]

the reason is that I've been using my brother in laws WhiBal gray card and it has stickers on it to help focus and determine glare. The free one I have has nothing on the grey side and I forgot that it won't focus.