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06-24-2015, 02:20 PM   #1
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I need focusing help please

I have had the k-3 for about a year. I know I can get images in focus, I have taken pictures of my kids where I can count eyebrow hairs. But then sometimes I get these images where it seems out of focus and I can't figure out why or what I did wrong. Recently I just switched to focus priority to make sure it wasn't user error, so I assume that means shutter won't go off if out of focus? I use back button focus. It looks like it focuses somewhere, but not where I am expecting. I use af.s, mostly manual mode. I have stuck the camera on a tripod, and manually focused the lens and got it to focus where I want and the images look fine. I use the expanded area auto focus or select just one focus point and I feel like it doesn't focus where I am expecting.

For example today I went out and took pictures of my kids at the playground. I swore I focused on the face, but it looks like her dress in more in focus than her face. Then another it looked like the equipment was more in focus. She wasn't moving around either, and my shutter speed was 1/250. I also took photos of a building where I didn't move and 2 images look out of focus.

I have asked this question before, took some tips, figured out some stuff (one time I had high iso noise reduction on) and I am fully confident I fixed the issue and know what went wrong and been happy for a while, then bam, focus off again, and I think WTF did I do? I have no clue. And it is so frustrating that I don't know why I get some random shots out of focus. I don't seem to have as much issue with my manual lens on the k-3, so I have to think it is some setting?

06-24-2015, 02:27 PM   #2
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First question. Are these out of focus issues mainly with wide open f/stops?

It is possible you have some front or back focus issues with some of your lenses. The AF system on the K3 while good is not perfect. Tuning it using AF fine adjustments could help. Some missed shots do happen and it is hard to take since you are not completely in charge and are at the mercy of the computer in your camera.
06-24-2015, 02:35 PM   #3
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set your focus to center, select the fastest aperture you have and take a close picture of a word on a newspaper from a 45deg angle several times in af and several times in mf and see if there is a difference
06-24-2015, 03:09 PM   #4
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QuoteOriginally posted by UncleVanya Quote
First question. Are these out of focus issues mainly with wide open f/stops?

It is possible you have some front or back focus issues with some of your lenses. The AF system on the K3 while good is not perfect. Tuning it using AF fine adjustments could help. Some missed shots do happen and it is hard to take since you are not completely in charge and are at the mercy of the computer in your camera.

no, I thought that might be an issue too, but I took photos of a building that were f/8 to f/14 at 48 and 53mm, I have the 18-135mm lens

---------- Post added 06-24-15 at 06:10 PM ----------

QuoteOriginally posted by Sliver-Surfer Quote
set your focus to center, select the fastest aperture you have and take a close picture of a word on a newspaper from a 45deg angle several times in af and several times in mf and see if there is a difference

Ok I will try that and post images

06-24-2015, 03:39 PM   #5
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Here is the standard list of questions:
  • Camera motion? With the K-3, this is a very prevalent cause of lapsed sharpness.
  • Subject motion? Usually self-evident.
  • Distant subject? The more air between you and the subject, the softer the image will be and the more difficult it is to acquire accurate focus.
  • Able to get sharp results using manual focus and focus peaking in magnified live view? Flat high contrast target and camera on tripod at 20x the focal length. If not, it is the lens. As you are probably aware, your 18-135 is not equally good at all focal lengths. The same is true of most zooms.
  • AF point other than on the subject?
  • AF system limitations exceeded? The dirty secret about PDAF (viewfinder AF system) is that it is not very precise, meaning that getting the correct focus plane twice in a row may prove difficult with many subjects. This is particularly true when the subject lacks contrast or when using a faster lens (say f/2.8) with other than the center AF column or with any lens faster than f/2.8 with any of the AF points.
  • AF point oriented to ambiguous element of subject? A curved receding surface (cheek in profile) is the textbook case for this one. Another is an element with significant changes in depth within the diameter of the focus point (orbit of the eye in profile).
  • AF point not oriented to the intended element of the subject? The camera cannot read your mind. If in "auto", it chooses the first thing that pops.
Notice that the above only applies to AF-S and that no mention is made of AF fine adjustments. AF-C is rather complicated and not useful for general troubleshooting. AF fine adjustment is not on the list because it is the standard cure-all suggestion, but is seldom the right answer. I have a bias though. It is my opinion that a 45-degree target and the AF adjust settings are pretty much a recipe for frustration, confusion and poor results and a 400 comment thread on the Pentax Forums.


Steve
06-24-2015, 03:44 PM   #6
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QuoteOriginally posted by Murfy Quote
Ok I will try that and post images
Forget the 45-degree angle. That only makes the task for the camera harder. Evaluate with the lens axis at right angles to the test target.


Steve
06-24-2015, 03:53 PM   #7
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QuoteOriginally posted by stevebrot Quote
Forget the 45-degree angle. That only makes the task for the camera harder. Evaluate with the lens axis at right angles to the test target.


Steve
I suspect the 45 mention was to show front/back focus errors by focusing on one line of type and seeing where the focus actually is.
06-24-2015, 04:02 PM   #8
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QuoteOriginally posted by Canada_Rockies Quote
I suspect the 45 mention was to show front/back focus errors by focusing on one line of type and seeing where the focus actually is.
Can issues like this happen with auto focus and not manual focus? My shots in manual spot are exactly where I thought I focused, but the ones I did with auto (I did spot, then auto then sel setting) were either focusing above or under. I am going to try this test again, along with 90 degree angle test, because this seems odd to me.

So I have done a bunch of tests with the camera on a tripod, and using manual and af, and it always looks like the manual is sharper. I went through af.s with spot, auto, sel and manual. When I ignored what the camera said was in focus for manual, I got the sharpest image.


Last edited by Murfy; 06-24-2015 at 04:56 PM.
06-24-2015, 07:56 PM   #9
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QuoteOriginally posted by Canada_Rockies Quote
I suspect the 45 mention was to show front/back focus errors by focusing on one line of type and seeing where the focus actually is.
Yes and in manual focus it would show focus screen shim maladjustment which can cause some user confusion with where the AF is focusing on
06-25-2015, 08:16 AM   #10
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QuoteOriginally posted by Murfy Quote
Can issues like this happen with auto focus and not manual focus? My shots in manual spot are exactly where I thought I focused, but the ones I did with auto (I did spot, then auto then sel setting) were either focusing above or under. I am going to try this test again, along with 90 degree angle test, because this seems odd to me.

So I have done a bunch of tests with the camera on a tripod, and using manual and af, and it always looks like the manual is sharper. I went through af.s with spot, auto, sel and manual. When I ignored what the camera said was in focus for manual, I got the sharpest image.
Murfy - dig out your manual and make a general AF adjustment to make any one of the manual lenses autofocus at the same point as your manual focus. This should solve your problem. Individual lenses may need an individual adjustment from that point.
06-25-2015, 08:25 AM   #11
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QuoteOriginally posted by Canada_Rockies Quote
Murfy - dig out your manual and make a general AF adjustment to make any one of the manual lenses autofocus at the same point as your manual focus. This should solve your problem. Individual lenses may need an individual adjustment from that point.
I did that earlier today it looks like -6 is what it needs to be on, I did some tests on a tripod and using a remote trigger. Then my battery was getting low, so once it charges, I will see if that works.
06-29-2015, 05:15 AM   #12
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I am still having issues and it seems to be at certain focal lengths, not extreme lengths, I expect that, but like anything over 50mm is in focus at another place than i focused on. But it's not the same. Sometimes it is back, sometimes it is in front.

I have a nikond200 with a sigma 18-250 lens and have never had issues like I am having with this, (also many years in film) so I am wondering if there is some issue with the lens, but I think it it is out of warranty by now? I am going to try to reset my camera and do one other thing to try. I took a bunch of photos yesterday and focus on a spot on the trunk of the tree. That was not in focus, but the leaves were. Very frustrating.

Last edited by Murfy; 06-29-2015 at 07:11 AM.
06-29-2015, 08:34 AM   #13
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If it is only the one lens, I would suspect the lens, but just in case, I would set the AF.S and use only the centre focus point. It may be that the problem is not helped by the lack of sharp contrast, and the camera is using other focus points that have higher contrast. This is a long shot, I know, but it did come to what is left of my mind this morning, and there isn't much left with a migraine. We are going to have some dandy thunderstorms today, I think.
06-29-2015, 11:50 AM   #14
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so I just took some more test shots. some were live view with focus peaking on. Took camera inside, stuck it on a tripod, focus peaking on, and loaded them into lightroom, and it is in focus somewhere else than what it was showing me. Used 2 different lens (one was manual focus) So this is a camera issue, I assume?
06-30-2015, 11:37 AM   #15
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I think I fixed it, and if anything thinks "no that is impossible" feel free to mention it, because I really want to find the cause. But what I did was really clean out the AF prism (I read that on another post) with a dust free cloth that I keep in a baggy for film negatives, I blew out dust in the focusing screen (but I added a hair, ugh!) and I reset everything. I took a bunch of photos and the only ones that are out of focus are slow shutter speed and other reasons I can probably explain. I had much many more photos in focus and in focus where I felt I focus. So maybe it just needed a good cleaning?

Last edited by Murfy; 07-01-2015 at 03:49 PM.
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