K-x with DA 40mm -- AF problem

jlaubza · 06-23-2011, 06:26 AM

First, Set the focusing points to center point only - this is not the same as spot metering. Set the exposure metering to matrix (the one which is not center weighted and not spot metering either).

Ensure that shake reduction is on.

Ensure good lighting.

Check the dipoter adjustment slider that you are seeing clearly - the best way to do that is to half press the shutter button while looking thru the VF. The camera data lights up at the bottom of the VF and you set the slider until the data is clearly focused.

Use a tripod to rule out hand shake or else use a high shutter speed, at least 1/350.

Now, the quick way to test - use the LV function but you must rest your camera on a table or use a tripod. When the LV focus is correct, switch it off without moving the camera and then check through the VF if the pix looks focused. If it is, then it it is your technique. If it isn't focused in the VF, then take your camera into an agent! Good luck.

love_myenla · 06-23-2011, 07:02 AM

Thanks for the suggestion.

I tried the method you mentioned, after I switched it off, it looks focused in the VF.
However, when I turned it on again to take the pix without moving the camera, the pix is not focused again.

Then I turned on the LV, same spot, same shutter speed... everything stays the same, it focused on the right object and the WB is somehow different. It's much brighter than the VF.
Should I take it into an agent then?

sirjes2 · 02-26-2012, 01:21 PM

Ok, so it's almost a year later, but I just checked this thread. So sorry. To answer your question, no. The kit lens is spot-on every time. Since I replied back in June, I've had a lot more time with the 40mm and found that it truly backfocuses a lot of the time. Even in daylight it will focus just a short distance behind my target. If I lift my finger and press halfway 1 or 2 more times, it will then focus properly.

Alizarine · 02-26-2012, 07:37 PM

the light on the subject seems to have changed from photo 1 to photo 2 (photo 1 has yellow - tungsten light?) are there other light sources aside from the one in the background?

It happens to my K-x too whatever lens I use, when the light coming in is tungsten (incandescent, yellow light). Though you mention it does not happen when you use the kit lens?

edit:

my, i didn't notice the date. I hope the OP had solved the problem already..

Last edited by Alizarine; 02-26-2012 at 07:44 PM.

Marc Sabatella · 02-26-2012, 10:29 PM

The example shots posted here don't demonstrate any problem that I can see, but perhaps you should post your own. The bottom line is that cameras don't read minds. You might wanted to focus on the face, but if you want the camera to know that, you can't just point in that general direction and hope. You need to select a specific focus point and then be sure to center it squarely on your subject, and be sure your subjects fills the entire area covered by the sensor.

sirjes2 · 12-19-2012, 03:01 PM

I attempted to sell the 40mm, but I'm glad no one replied. I recently purchased the K5II and it's not only an amazing update from my Kx, but it focuses perfectly with the 40mm limited attached. I tried going back and forth between the kx and k5 with this lens attached and I could tell in the LCD during playback that although the K5II was sharp, the KX continued to backfocus. I contacted Pentax and they said that they were not aware of any issues, but they could calibrate the Kx with the 40mm if I wanted to pay for shipping and repairs. I laughed at the thought of paying for something that should already work. Instead, I'm selling the Kx with the kit lenses which still work fine.

Side note: Here is an example of the backfocus. I was using single/spot AF and aiming at the cheese balls in the bowl.

sirjes2 · 12-19-2012, 03:01 PM

oh, this was recomposed, btw.

**7samurai** · 12-20-2012, 12:20 AM

I have a K-x and the 40mm XS. I can tell you on my camera it will back focus alot. I have to enter the debug menu to add +100 adjustment to correct the issue. My 35mm f/2.4 needs 120 adjustment. My kit lenses need 0 adjustment. Having only 1 universal adjustment for is frustrating. When I switch lenses, I have to re-enter debug so I can make adjustments.

trevorgrout · 12-20-2012, 06:10 AM

I have the k-x and the DA 40 and I also noticed backfocusing when using the DA 40. Entered a +30 in debug mode and now it focuses perfect. The DA40 is a great little lens!

sirjes2 · 12-20-2012, 02:45 PM

I wish someone would have mentioned debug mode. I've never attempted it before and sounds like it would have been useful.

02-26-2012, 01:21 PM	#18
sirjes2 New Member Join Date: Jun 2011 Photos: Gallery Posts: 21	My apologies Ok, so it's almost a year later, but I just checked this thread. So sorry. To answer your question, no. The kit lens is spot-on every time. Since I replied back in June, I've had a lot more time with the 40mm and found that it truly backfocuses a lot of the time. Even in daylight it will focus just a short distance behind my target. If I lift my finger and press halfway 1 or 2 more times, it will then focus properly.

12-19-2012, 03:01 PM	#21
sirjes2 New Member Join Date: Jun 2011 Photos: Gallery Posts: 21	Update I attempted to sell the 40mm, but I'm glad no one replied. I recently purchased the K5II and it's not only an amazing update from my Kx, but it focuses perfectly with the 40mm limited attached. I tried going back and forth between the kx and k5 with this lens attached and I could tell in the LCD during playback that although the K5II was sharp, the KX continued to backfocus. I contacted Pentax and they said that they were not aware of any issues, but they could calibrate the Kx with the 40mm if I wanted to pay for shipping and repairs. I laughed at the thought of paying for something that should already work. Instead, I'm selling the Kx with the kit lenses which still work fine. Side note: Here is an example of the backfocus. I was using single/spot AF and aiming at the cheese balls in the bowl.

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06-23-2011, 06:26 AM	#16
jlaubza Senior Member Join Date: Jul 2008 Location: south africa, johannesburg Photos: Gallery Posts: 228	First, Set the focusing points to center point only - this is not the same as spot metering. Set the exposure metering to matrix (the one which is not center weighted and not spot metering either). Ensure that shake reduction is on. Ensure good lighting. Check the dipoter adjustment slider that you are seeing clearly - the best way to do that is to half press the shutter button while looking thru the VF. The camera data lights up at the bottom of the VF and you set the slider until the data is clearly focused. Use a tripod to rule out hand shake or else use a high shutter speed, at least 1/350. Now, the quick way to test - use the LV function but you must rest your camera on a table or use a tripod. When the LV focus is correct, switch it off without moving the camera and then check through the VF if the pix looks focused. If it is, then it it is your technique. If it isn't focused in the VF, then take your camera into an agent! Good luck.

06-23-2011, 07:02 AM	#17
love_myenla New Member Join Date: Apr 2011 Posts: 8 Original Poster	Thanks for the suggestion. I tried the method you mentioned, after I switched it off, it looks focused in the VF. However, when I turned it on again to take the pix without moving the camera, the pix is not focused again. Then I turned on the LV, same spot, same shutter speed... everything stays the same, it focused on the right object and the WB is somehow different. It's much brighter than the VF. Should I take it into an agent then?

02-26-2012, 07:37 PM	#19
Alizarine Veteran Member Join Date: Dec 2010 Location: Manila Photos: Gallery \| Albums Posts: 2,185	the light on the subject seems to have changed from photo 1 to photo 2 (photo 1 has yellow - tungsten light?) are there other light sources aside from the one in the background? It happens to my K-x too whatever lens I use, when the light coming in is tungsten (incandescent, yellow light). Though you mention it does not happen when you use the kit lens? edit: my, i didn't notice the date. I hope the OP had solved the problem already.. Last edited by Alizarine; 02-26-2012 at 07:44 PM.

02-26-2012, 10:29 PM	#20
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	The example shots posted here don't demonstrate any problem that I can see, but perhaps you should post your own. The bottom line is that cameras don't read minds. You might wanted to focus on the face, but if you want the camera to know that, you can't just point in that general direction and hope. You need to select a specific focus point and then be sure to center it squarely on your subject, and be sure your subjects fills the entire area covered by the sensor.

12-19-2012, 03:01 PM	#22
sirjes2 New Member Join Date: Jun 2011 Photos: Gallery Posts: 21	oh, this was recomposed, btw.

12-20-2012, 12:20 AM	#23
7samurai Site Supporter Join Date: Apr 2010 Location: Rancho Cucamonga, CA Photos: Albums Posts: 474	I have a K-x and the 40mm XS. I can tell you on my camera it will back focus alot. I have to enter the debug menu to add +100 adjustment to correct the issue. My 35mm f/2.4 needs 120 adjustment. My kit lenses need 0 adjustment. Having only 1 universal adjustment for is frustrating. When I switch lenses, I have to re-enter debug so I can make adjustments.

12-20-2012, 06:10 AM	#24
trevorgrout Senior Member Join Date: Mar 2010 Location: Oklahoma City Photos: Albums Posts: 105	I have the k-x and the DA 40 and I also noticed backfocusing when using the DA 40. Entered a +30 in debug mode and now it focuses perfect. The DA40 is a great little lens!

12-20-2012, 02:45 PM	#25
sirjes2 New Member Join Date: Jun 2011 Photos: Gallery Posts: 21	I wish someone would have mentioned debug mode. I've never attempted it before and sounds like it would have been useful.