Why is autofocus not consistent on my K-X?

Marc Sabatella · 05-14-2011, 10:54 PM

Feel free to post examples showing these problems. In some cases, actual camera or lens defects exist, and they can be fixed. In other cases - the majority of reports by far - it's user error. Only by posting pictures will anyone be able to tell which is the case.

jlaubza · 06-11-2011, 04:02 AM

A somewhat delayed follow up but at last, I have proven to my satisfaction that the K-X has auto focusing problems, or least mine has.

On a recent trip to a country lodge, we had a friend along who had just received a new K-R as a gift. I was trying out my Pentax 55 - 300mm lens on a distant target to check image sharpness - most (not all) of the auto focus shots were blurred (I was using a tripod with mirror lock up and remote actuation). Blurring was mostly due to front focus but the target I was using filled the center spot of the VF - I use center point focus.

I switched to manual focus and got more consistent results (I defocused the lens between every shot). Then I placed the lens on my GX10 - auto focus was spot on every time.

I then tried the lens on the new K-R - not only was autofocus nailing the focus but it was fast and didn't go through the hunting routine that is common on my K-X.

The camera was set to sunlight WB - conditions were late afternoon and the target was in the shade.

I tried the K-X and same lens the next day on a different target, still using a tripod and mirror lockup agin in the late afternoon - this time AF was OK.

So, conclusion, the K-R's new SAFOX 9 AF module is doing a much better job than the SAFOX 8 AF module on the K-X, which is worse than whatever module was fitted to the K10D/GX10 range. Strange that the older camera did a better job on AF.

And as a bonus, the K-R pulled focus in near dark conditions while the K-X couldn't. I'm tempted to upgrade to the K-R!

Andyvious · 06-11-2011, 02:13 PM

Anyone of you with AF issues updated the firmware and tried it again?

Just wondering...

bwDraco · 06-11-2011, 04:54 PM

Originally posted by jlaubza

A somewhat delayed follow up but at last, I have proven to my satisfaction that the K-X has auto focusing problems, or least mine has.

On a recent trip to a country lodge, we had a friend along who had just received a new K-R as a gift. I was trying out my Pentax 55 - 300mm lens on a distant target to check image sharpness - most (not all) of the auto focus shots were blurred (I was using a tripod with mirror lock up and remote actuation). Blurring was mostly due to front focus but the target I was using filled the center spot of the VF - I use center point focus.

I switched to manual focus and got more consistent results (I defocused the lens between every shot). Then I placed the lens on my GX10 - auto focus was spot on every time.

I then tried the lens on the new K-R - not only was autofocus nailing the focus but it was fast and didn't go through the hunting routine that is common on my K-X.

The camera was set to sunlight WB - conditions were late afternoon and the target was in the shade.

I tried the K-X and same lens the next day on a different target, still using a tripod and mirror lockup agin in the late afternoon - this time AF was OK.

So, conclusion, the K-R's new SAFOX 9 AF module is doing a much better job than the SAFOX 8 AF module on the K-X, which is worse than whatever module was fitted to the K10D/GX10 range. Strange that the older camera did a better job on AF.

And as a bonus, the K-R pulled focus in near dark conditions while the K-X couldn't. I'm tempted to upgrade to the K-R!

From what you've written, it's pretty clear that your K-x has a defective AF system. The GX-10/K10D has the same SAFOX VIII AF system as the K-x. If the K-x is consistently having trouble focusing correctly, have it serviced or attempt to correct it yourself.

While my K-r has a minor front-focus problem that generally only shows up at close range, it focuses correctly in the vast majority of shots and most of my pictures come out sharp.

FrumPilot · 06-12-2011, 09:14 PM

I too was disapointed with my k-x especially with a third party lens. I got much better results with the pentax lenses.
I understand though that most cameras don't nail it all the time.
Jake

yusuf · 06-14-2011, 03:05 AM

Well, it's hard for me to believe K10D has better AF than k-x as I have used both. I am not a great fan of Pentax AF in general but IMHO k-x AF is far better than all the previous cameras including K10D.

I am not saying that I don't get missed shots - but that was true with my K10D and K100D too. In fact, it was nearly impossible to nail AF with previous camera where k-x really tries hard and even nails it many time. One thing I always do it to focus at long distance and then focus on subject and most of the time it works. Also, I have not seen any difference between Pentax or third party lenses as far as AF accuracy is concern. Here is a shot with with K-x with third party lens (Tamron 28-75mm )

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05-14-2011, 10:54 PM	#31
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Feel free to post examples showing these problems. In some cases, actual camera or lens defects exist, and they can be fixed. In other cases - the majority of reports by far - it's user error. Only by posting pictures will anyone be able to tell which is the case.

06-11-2011, 04:02 AM	#32
jlaubza Senior Member Join Date: Jul 2008 Location: south africa, johannesburg Photos: Gallery Posts: 228 Original Poster	A somewhat delayed follow up but at last, I have proven to my satisfaction that the K-X has auto focusing problems, or least mine has. On a recent trip to a country lodge, we had a friend along who had just received a new K-R as a gift. I was trying out my Pentax 55 - 300mm lens on a distant target to check image sharpness - most (not all) of the auto focus shots were blurred (I was using a tripod with mirror lock up and remote actuation). Blurring was mostly due to front focus but the target I was using filled the center spot of the VF - I use center point focus. I switched to manual focus and got more consistent results (I defocused the lens between every shot). Then I placed the lens on my GX10 - auto focus was spot on every time. I then tried the lens on the new K-R - not only was autofocus nailing the focus but it was fast and didn't go through the hunting routine that is common on my K-X. The camera was set to sunlight WB - conditions were late afternoon and the target was in the shade. I tried the K-X and same lens the next day on a different target, still using a tripod and mirror lockup agin in the late afternoon - this time AF was OK. So, conclusion, the K-R's new SAFOX 9 AF module is doing a much better job than the SAFOX 8 AF module on the K-X, which is worse than whatever module was fitted to the K10D/GX10 range. Strange that the older camera did a better job on AF. And as a bonus, the K-R pulled focus in near dark conditions while the K-X couldn't. I'm tempted to upgrade to the K-R!

06-11-2011, 02:13 PM	#33
Andyvious Inactive Account Join Date: Jun 2011 Location: Montreal Posts: 17	Anyone of you with AF issues updated the firmware and tried it again? Just wondering...

06-11-2011, 04:54 PM	#34
bwDraco Veteran Member Join Date: Jul 2010 Location: New York Photos: Albums Posts: 1,071	Originally posted by jlaubza A somewhat delayed follow up but at last, I have proven to my satisfaction that the K-X has auto focusing problems, or least mine has. On a recent trip to a country lodge, we had a friend along who had just received a new K-R as a gift. I was trying out my Pentax 55 - 300mm lens on a distant target to check image sharpness - most (not all) of the auto focus shots were blurred (I was using a tripod with mirror lock up and remote actuation). Blurring was mostly due to front focus but the target I was using filled the center spot of the VF - I use center point focus. I switched to manual focus and got more consistent results (I defocused the lens between every shot). Then I placed the lens on my GX10 - auto focus was spot on every time. I then tried the lens on the new K-R - not only was autofocus nailing the focus but it was fast and didn't go through the hunting routine that is common on my K-X. The camera was set to sunlight WB - conditions were late afternoon and the target was in the shade. I tried the K-X and same lens the next day on a different target, still using a tripod and mirror lockup agin in the late afternoon - this time AF was OK. So, conclusion, the K-R's new SAFOX 9 AF module is doing a much better job than the SAFOX 8 AF module on the K-X, which is worse than whatever module was fitted to the K10D/GX10 range. Strange that the older camera did a better job on AF. And as a bonus, the K-R pulled focus in near dark conditions while the K-X couldn't. I'm tempted to upgrade to the K-R! From what you've written, it's pretty clear that your K-x has a defective AF system. The GX-10/K10D has the same SAFOX VIII AF system as the K-x. If the K-x is consistently having trouble focusing correctly, have it serviced or attempt to correct it yourself. While my K-r has a minor front-focus problem that generally only shows up at close range, it focuses correctly in the vast majority of shots and most of my pictures come out sharp.

06-12-2011, 09:14 PM	#35
FrumPilot Inactive Account Join Date: Apr 2011 Posts: 55	I too was disapointed with my k-x especially with a third party lens. I got much better results with the pentax lenses. I understand though that most cameras don't nail it all the time. Jake

06-14-2011, 03:05 AM	#36
yusuf Pentaxian Join Date: Nov 2008 Location: Palo Alto, CA Photos: Gallery Posts: 2,497	Well, it's hard for me to believe K10D has better AF than k-x as I have used both. I am not a great fan of Pentax AF in general but IMHO k-x AF is far better than all the previous cameras including K10D. I am not saying that I don't get missed shots - but that was true with my K10D and K100D too. In fact, it was nearly impossible to nail AF with previous camera where k-x really tries hard and even nails it many time. One thing I always do it to focus at long distance and then focus on subject and most of the time it works. Also, I have not seen any difference between Pentax or third party lenses as far as AF accuracy is concern. Here is a shot with with K-x with third party lens (Tamron 28-75mm )