K-x issues with autofocus

moshepupkin · 09-09-2012, 06:50 AM

Hi there,

I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus. Usually moving a camera a little bit helps, but sometimes no matter what I do it simply would not autofocus!

What's wrong?

**THoog** · 09-09-2012, 07:28 AM

That lens can be a little soft wide open. It sounds like your copy is just soft enough to give the AF system problems. My K-r also has problems focusing with the Tamron 17-50 f2.8 (but my K-x did not, or had less noticeable problems, and my K100D never had problems with it). It seemed to do much better when I switched to AF.S (single-shot) mode. AF.A and AF.C almost always missed focus. You could also try setting the AF to center-point focusing to see if that helps.

**crewl1** · 09-09-2012, 07:37 AM

Try cleaning the contacts on both camera and lens mounts to see if it helps.

moshepupkin · 09-11-2012, 08:27 AM

I've also noticed that sometimes the camera would switch from AF to MF and vice versa even though it is set to AF! How can it be!?

moshepupkin · 09-12-2012, 12:42 AM

BTW, non of the above suggestions helped much. Any other ideas? I don't even know if this is a problem that can be repaired or not, or if this a camera or lenses problem...

**crewl1** · 09-12-2012, 07:51 AM

Originally posted by moshepupkin

or if this a camera or lenses problem.

If other lenses work fine then it is a lens problem. If all lenses act the same way then it is a camera problem. Have you tried other lenses?

Alizarine · 09-12-2012, 08:38 AM

Originally posted by moshepupkin

Hi there, I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus. Usually moving a camera a little bit helps, but sometimes no matter what I do it simply would not autofocus! What's wrong?

Originally posted by moshepupkin

I've also noticed that sometimes the camera would switch from AF to MF and vice versa even though it is set to AF! How can it be!?

When did you buy your camera? Mine was circa 2010, and I'm encountering similar problems. I figured out a solution though I am not sure if it is the same for your problem. There are a few things you need to make sure first:

1. The problem is that the focus gets stuck at either MF or AF, regardless of, for example, the switch was set to AF and the display says "MF" or when the switch is at "MF" but the display (and active focus mechanism) is still AF.

2. Clean all contacts on the camera mount. DO NOT use any liquid cleaning agent, a clean microfiber cloth will do.

3. That the problem exists on all lenses you mount on your K-x.
...Check the screwdrive screw with the lens off- it should be perfectly centered in the hole it comes in and out of. A little difference won't matter, but if it, say, skids along the edges when it pops out of the body (in AF mode), have a Pentax technician check it.

4. Check the switch - remove the lens first. When you switch the focus switch to AF, the screwdrive screw should pop out of the body. In MF, it should sink into the body. Also, while in AF mode, the screw should be able to sink into the body given some pressure - this ensures that the spring underneath it is not damaged.

5. If all things are how they should be as in #4, carefully move the switch between the modes. You should feel something like a slight semi-click before it moves fully down or up. This means that somehow, one of the contacts that confirm that the camera has switched AF modes has loosened up or is not aligning properly. This solution will work but you have to be very careful in switching from now on, if you want to avoid spending on body repair.

IF the AF works properly on other lenses, then it's one or other particular lenses your K-x is having problems communicating with. If #5 does not solve the problem, have an authorized (or otherwise very knowledgeable) camera technician check it.

The screwdrive AF problem also should not affect your camera's ability to use the AF of KAF3/SDM lenses

Last edited by Alizarine; 09-12-2012 at 09:59 AM.

audiobomber · 09-12-2012, 08:44 AM

Originally posted by moshepupkin

I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus.

I don't understand the problem from your description. Do you mean it doesn't try to focus at all, or that it tries, but can't achieve focus lock (i.e. hunts)? If the former, it sounds like the camera or camera/lens interface, if the latter I would suspect the lens.

Originally posted by crewl1

If other lenses work fine then it is a lens problem. If all lenses act the same way then it is a camera issue. Have you tried other lenses?

Diagnosing whether it's the camera or lens is definitely the best place to start.

moshepupkin · 09-13-2012, 02:02 PM

Originally posted by audiobomber

I don't understand the problem from your description. Do you mean it doesn't try to focus at all, or that it tries, but can't achieve focus lock (i.e. hunts)?

In the cases when the camera cannot achieve a focus lock, I've noticed that it keeps switching spontaneously from AF to MF, according to what is displayed on the screen.

09-09-2012, 06:50 AM	#1
moshepupkin Inactive Account Join Date: May 2010 Posts: 37	K-x issues with autofocus Hi there, I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus. Usually moving a camera a little bit helps, but sometimes no matter what I do it simply would not autofocus! What's wrong?

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09-09-2012, 07:28 AM	#2
THoog Loyal Site Supporter Join Date: Aug 2012 Location: North Carolina Photos: Gallery \| Albums Posts: 3,685	That lens can be a little soft wide open. It sounds like your copy is just soft enough to give the AF system problems. My K-r also has problems focusing with the Tamron 17-50 f2.8 (but my K-x did not, or had less noticeable problems, and my K100D never had problems with it). It seemed to do much better when I switched to AF.S (single-shot) mode. AF.A and AF.C almost always missed focus. You could also try setting the AF to center-point focusing to see if that helps.

09-09-2012, 07:37 AM	#3
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	Try cleaning the contacts on both camera and lens mounts to see if it helps.

09-11-2012, 08:27 AM	#4
moshepupkin Inactive Account Join Date: May 2010 Posts: 37 Original Poster	I've also noticed that sometimes the camera would switch from AF to MF and vice versa even though it is set to AF! How can it be!?

09-12-2012, 12:42 AM	#5
moshepupkin Inactive Account Join Date: May 2010 Posts: 37 Original Poster	BTW, non of the above suggestions helped much. Any other ideas? I don't even know if this is a problem that can be repaired or not, or if this a camera or lenses problem...

09-12-2012, 07:51 AM	#6
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	Originally posted by moshepupkin or if this a camera or lenses problem. If other lenses work fine then it is a lens problem. If all lenses act the same way then it is a camera problem. Have you tried other lenses?

09-12-2012, 08:38 AM	#7
Alizarine Veteran Member Join Date: Dec 2010 Location: Manila Photos: Gallery \| Albums Posts: 2,185	Originally posted by moshepupkin Hi there, I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus. Usually moving a camera a little bit helps, but sometimes no matter what I do it simply would not autofocus! What's wrong? Originally posted by moshepupkin I've also noticed that sometimes the camera would switch from AF to MF and vice versa even though it is set to AF! How can it be!? When did you buy your camera? Mine was circa 2010, and I'm encountering similar problems. I figured out a solution though I am not sure if it is the same for your problem. There are a few things you need to make sure first: 1. The problem is that the focus gets stuck at either MF or AF, regardless of, for example, the switch was set to AF and the display says "MF" or when the switch is at "MF" but the display (and active focus mechanism) is still AF. 2. Clean all contacts on the camera mount. DO NOT use any liquid cleaning agent, a clean microfiber cloth will do. 3. That the problem exists on all lenses you mount on your K-x. ...Check the screwdrive screw with the lens off- it should be perfectly centered in the hole it comes in and out of. A little difference won't matter, but if it, say, skids along the edges when it pops out of the body (in AF mode), have a Pentax technician check it. 4. Check the switch - remove the lens first. When you switch the focus switch to AF, the screwdrive screw should pop out of the body. In MF, it should sink into the body. Also, while in AF mode, the screw should be able to sink into the body given some pressure - this ensures that the spring underneath it is not damaged. 5. If all things are how they should be as in #4, carefully move the switch between the modes. You should feel something like a slight semi-click before it moves fully down or up. This means that somehow, one of the contacts that confirm that the camera has switched AF modes has loosened up or is not aligning properly. This solution will work but you have to be very careful in switching from now on, if you want to avoid spending on body repair. IF the AF works properly on other lenses, then it's one or other particular lenses your K-x is having problems communicating with. If #5 does not solve the problem, have an authorized (or otherwise very knowledgeable) camera technician check it. The screwdrive AF problem also should not affect your camera's ability to use the AF of KAF3/SDM lenses Last edited by Alizarine; 09-12-2012 at 09:59 AM.

09-12-2012, 08:44 AM	#8
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by moshepupkin I'm having a problem with autofocus on my k-x camera with Tamron 17-50mm F2.8 lenses. Basically the problem is - in about 50% of the times I'm trying to take a picture the autofocus does not work, I mean it simply refuses to focus. I don't understand the problem from your description. Do you mean it doesn't try to focus at all, or that it tries, but can't achieve focus lock (i.e. hunts)? If the former, it sounds like the camera or camera/lens interface, if the latter I would suspect the lens. Originally posted by crewl1 If other lenses work fine then it is a lens problem. If all lenses act the same way then it is a camera issue. Have you tried other lenses? Diagnosing whether it's the camera or lens is definitely the best place to start.

09-13-2012, 02:02 PM	#9
moshepupkin Inactive Account Join Date: May 2010 Posts: 37 Original Poster	Originally posted by audiobomber I don't understand the problem from your description. Do you mean it doesn't try to focus at all, or that it tries, but can't achieve focus lock (i.e. hunts)? In the cases when the camera cannot achieve a focus lock, I've noticed that it keeps switching spontaneously from AF to MF, according to what is displayed on the screen.