Dirty autofocus sensor

semaca · 01-30-2018, 06:39 AM

Lately I had some problems with my K-3 and many of my photos were blurry and the autofocus was really BAD even in daylight. Did some test shot with a focus chart and I suspected that the lens had some back/frontfocus issues.

Well, on the lens of the autofocus sensor I found a hair or some kind of clothing thread and I hope that thing was the origin of all my problems. Does anybody know if that 3cm hair can mess the autofocus that much?

08amczb · 01-30-2018, 07:00 AM

It can mess definitly.

I had only dust on it and even that messed up the autofocus.

**savoche** · 01-30-2018, 07:14 AM

Originally posted by 08amczb

I had only dust on it and even that messed up the autofocus.

Same story here. Or at least my focus problems went away after a few blasts with the rocket blower in the direction of the focus sensor.

photoptimist · 01-30-2018, 09:44 AM

Me three! I had an eyelash on the AF sensor lens that caused huge AF reliability issues. I thought the camera was broken until I found the culprit.

Now I always use a rocketblower to clean out the mirror box and AF sensor area when I do a sensor cleaning.

**twilhelm** · 01-30-2018, 02:37 PM

I can attest to this also. Before my last wedding, I did a thorough cleaning of my K5 and K3 with a blower. I noticed significant improvements in autofocus, especially with my K5. And for me, it was only dust.

randomstuff · 01-30-2018, 04:18 PM

It can, but did you check the mirror and secondary mirror for grease spots?
That's another culrpit and some cameras have this issue. My K-3 did and it was a pain to clean.

Imgur: The magic of the Internet

semaca · 01-31-2018, 09:07 AM

Originally posted by randomstuff

It can, but did you check the mirror and secondary mirror for grease spots?
That's another culrpit and some cameras have this issue. My K-3 did and it was a pain to clean.

Imgur: The magic of the Internet

I will check for that tonight, but do I have to manually move the mirror to get to the secondary one?

The bad thing was that I always clean my camera at someone else, but now I will buy a cleaning kit.

kjphilippona · 01-31-2018, 09:18 AM

Just were is the focus sensor located on the K3 and K1 ?

photoptimist · 01-31-2018, 09:37 AM

Originally posted by kjphilippona

Just were is the focus sensor located on the K3 and K1 ?

It's in the middle of the floor of the mirrorbox and looks up toward a secondary mirror that is behind the big reflex mirror.

kjphilippona · 01-31-2018, 10:46 AM

Had no idea all that was behind the reflex mirror. Another dumb question, just how do you get to the sensor and secondary mirror? When I select sensor clean the main reflex mirror goes up and all you see is that big beautiful Sony image sensor

randomstuff · 01-31-2018, 05:23 PM

Originally posted by kjphilippona

Had no idea all that was behind the reflex mirror. Another dumb question, just how do you get to the sensor and secondary mirror? When I select sensor clean the main reflex mirror goes up and all you see is that big beautiful Sony image sensor

http://mattgrum.com/photo_se/AF-Optics-Cutaway.png

You have to delicately lift it with your finger, ideally with nitrile gloves, so you don't leave any residue, grease or skin bits. There is a step in which secondary mirror snaps up to fold within the main mirror, but there is a range of angles at which you can see both mirrors.

I would caution about cleaning the mirror though. I did it and it works fine, but the mirror coating is not supposed to be very durable, so just read up on it if you are ok taking the risk. I had no choice, b.c. my camera was basically unusable with all this grease, and fixing it was basically the same cost as getting a new one.

kjphilippona · 01-31-2018, 05:28 PM - **1 Like**

Thank you randomstuff

randomstuff · 01-31-2018, 05:33 PM - **1 Like**

Originally posted by semaca

I will check for that tonight, but do I have to manually move the mirror to get to the secondary one?

The bad thing was that I always clean my camera at someone else, but now I will buy a cleaning kit.

Yes, manually is the only way I know. If you do a significant amount of grease ask at the place where you typically getting it cleaned, if they would do that. Mirrors are delicate and most people would advise against messing with them.
My local photography store wouldn't touch it for example, and told me I have to send it in... for $300 bucks plus shipping on a K-3 with 50k actuations. wasn't worth it.

I also saw it on an old D700 and heard some older canon 6Ds had this issue. So I guess it happens to some. I even wonder if this could be the reason why some people think K-3 AF is great, while others think its inaccurate. Mine started accurate and got worse over time, so I started digging.

---------- Post added 01-31-18 at 06:37 PM ----------

btw. more info on the subject from when I dealt with it:
autofocus inaccuracy, green spots on the mirror? - PentaxForums.com

01-30-2018, 06:39 AM	#1
semaca Senior Member Join Date: Nov 2014 Location: RO Posts: 143	Dirty autofocus sensor Lately I had some problems with my K-3 and many of my photos were blurry and the autofocus was really BAD even in daylight. Did some test shot with a focus chart and I suspected that the lens had some back/frontfocus issues. Well, on the lens of the autofocus sensor I found a hair or some kind of clothing thread and I hope that thing was the origin of all my problems. Does anybody know if that 3cm hair can mess the autofocus that much?

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01-30-2018, 07:00 AM	#2
08amczb Veteran Member Join Date: Dec 2013 Posts: 796	It can mess definitly. I had only dust on it and even that messed up the autofocus.

01-30-2018, 07:14 AM	#3
savoche Master of the obvious Join Date: Jun 2011 Location: Lowlands of Norway Posts: 18,312	Originally posted by 08amczb I had only dust on it and even that messed up the autofocus. Same story here. Or at least my focus problems went away after a few blasts with the rocket blower in the direction of the focus sensor.

01-30-2018, 09:44 AM	#4
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,129	Me three! I had an eyelash on the AF sensor lens that caused huge AF reliability issues. I thought the camera was broken until I found the culprit. Now I always use a rocketblower to clean out the mirror box and AF sensor area when I do a sensor cleaning.

01-30-2018, 02:37 PM	#5
twilhelm Loyal Site Supporter Join Date: Feb 2009 Location: Florida Photos: Gallery \| Albums Posts: 2,369	I can attest to this also. Before my last wedding, I did a thorough cleaning of my K5 and K3 with a blower. I noticed significant improvements in autofocus, especially with my K5. And for me, it was only dust.

01-30-2018, 04:18 PM	#6
randomstuff Junior Member Join Date: Aug 2017 Posts: 37	It can, but did you check the mirror and secondary mirror for grease spots? That's another culrpit and some cameras have this issue. My K-3 did and it was a pain to clean. Imgur: The magic of the Internet

01-31-2018, 09:07 AM	#7
semaca Senior Member Join Date: Nov 2014 Location: RO Posts: 143 Original Poster	Originally posted by randomstuff It can, but did you check the mirror and secondary mirror for grease spots? That's another culrpit and some cameras have this issue. My K-3 did and it was a pain to clean. Imgur: The magic of the Internet I will check for that tonight, but do I have to manually move the mirror to get to the secondary one? The bad thing was that I always clean my camera at someone else, but now I will buy a cleaning kit.

01-31-2018, 09:18 AM	#8
kjphilippona Veteran Member Join Date: Dec 2014 Location: Enterprise, Alabama Photos: Gallery \| Albums Posts: 1,298	Just were is the focus sensor located on the K3 and K1 ?

01-31-2018, 09:37 AM	#9
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,129	Originally posted by kjphilippona Just were is the focus sensor located on the K3 and K1 ? It's in the middle of the floor of the mirrorbox and looks up toward a secondary mirror that is behind the big reflex mirror.

01-31-2018, 10:46 AM	#10
kjphilippona Veteran Member Join Date: Dec 2014 Location: Enterprise, Alabama Photos: Gallery \| Albums Posts: 1,298	Had no idea all that was behind the reflex mirror. Another dumb question, just how do you get to the sensor and secondary mirror? When I select sensor clean the main reflex mirror goes up and all you see is that big beautiful Sony image sensor

01-31-2018, 05:23 PM	#11
randomstuff Junior Member Join Date: Aug 2017 Posts: 37	Originally posted by kjphilippona Had no idea all that was behind the reflex mirror. Another dumb question, just how do you get to the sensor and secondary mirror? When I select sensor clean the main reflex mirror goes up and all you see is that big beautiful Sony image sensor http://mattgrum.com/photo_se/AF-Optics-Cutaway.png You have to delicately lift it with your finger, ideally with nitrile gloves, so you don't leave any residue, grease or skin bits. There is a step in which secondary mirror snaps up to fold within the main mirror, but there is a range of angles at which you can see both mirrors. I would caution about cleaning the mirror though. I did it and it works fine, but the mirror coating is not supposed to be very durable, so just read up on it if you are ok taking the risk. I had no choice, b.c. my camera was basically unusable with all this grease, and fixing it was basically the same cost as getting a new one.

01-31-2018, 05:28 PM - 1 Like	#12
kjphilippona Veteran Member Join Date: Dec 2014 Location: Enterprise, Alabama Photos: Gallery \| Albums Posts: 1,298	Thank you randomstuff

01-31-2018, 05:33 PM - 1 Like	#13
randomstuff Junior Member Join Date: Aug 2017 Posts: 37	Originally posted by semaca I will check for that tonight, but do I have to manually move the mirror to get to the secondary one? The bad thing was that I always clean my camera at someone else, but now I will buy a cleaning kit. Yes, manually is the only way I know. If you do a significant amount of grease ask at the place where you typically getting it cleaned, if they would do that. Mirrors are delicate and most people would advise against messing with them. My local photography store wouldn't touch it for example, and told me I have to send it in... for $300 bucks plus shipping on a K-3 with 50k actuations. wasn't worth it. I also saw it on an old D700 and heard some older canon 6Ds had this issue. So I guess it happens to some. I even wonder if this could be the reason why some people think K-3 AF is great, while others think its inaccurate. Mine started accurate and got worse over time, so I started digging. ---------- Post added 01-31-18 at 06:37 PM ---------- btw. more info on the subject from when I dealt with it: autofocus inaccuracy, green spots on the mirror? - PentaxForums.com