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09-01-2012, 10:42 AM   #1
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Focusing issues with K-5 & 35/2.4?

I love this K-5 but I have noticed that when taking photos of 3 more people on the same focal plane the 35/2.4 seems to miss focus alot. It beeps and takes the shot but after I review it on the screen it looks off. I posted an example below which has not been processed. I don't seem to have the same issue with my Tamron 70-200 or my Sigma 10-20 3.5 lens. It seems the girl on the left is in focus but the girl on the right looks OOF. Do I need to do an AF adjustment?


Last edited by treebeard; 05-09-2013 at 04:24 PM.
09-01-2012, 11:04 AM   #2
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From what I can see on my phone, you may need an adjustment, but another possible culprit could be the shallow DOF. What aperture was this shot at?
09-01-2012, 11:13 AM   #3
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f/2.4. I have also shot at f/4 and had the same problem. I think I may need to do an AF adjustment. The issue only appears to be with my 35/2.4.
09-01-2012, 11:57 AM   #4
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@ f/2.4 and that looks like say 4 feet distance you have about 4.5" depth of focus. Could easily be that much variance in distance if the subjects are not perfectly aligned to your plane of senor. Hard to tell exactly but it looks like there might be 10-12" difference between tip of nose on left girl versus right girl.

Which might be why you only see it when you have 3 or people in a picture, easier to get all the noses lined up with only 1 or 2 people.

Best way to check is to take some pictures of a brick wall with the camera on a tripod and perfectly aligned with sensor parallel to the wall.

09-01-2012, 12:04 PM   #5
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I am going to download a chart and test the AF to see if I need to do an adjustment. Perhaps you are right about the distance and the difference.
09-01-2012, 12:46 PM   #6
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If you want to shoot a group of people at f2.4 and have them all in focus, you need to make sure they are all at an equal distance from the camera.
09-01-2012, 02:25 PM   #7
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QuoteOriginally posted by treebeard Quote
I am going to download a chart and test the AF to see if I need to do an adjustment. Perhaps you are right about the distance and the difference.
Also, test with the brick wall. The chart will test the AF and the center of the lens but may not be able to show you if the lens has issues on one side or the other. Flat wall, perfectly aligned with the sensor should show in focus all across the image, or at least evenly out of focus across the image. But I'm betting one of the girls was not lined up with the others.
09-01-2012, 03:43 PM   #8
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You are probably right, I am expecting more from the lens than I should be. I guess I have to remember the shallow DOF along with having SR off (I think I read it should be off?) does not make for a good combo if the people are not all in the same plane.

09-01-2012, 04:06 PM   #9
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QuoteOriginally posted by treebeard Quote
I am expecting more from the lens than I should be.
Shallow DOF isn't a lens fault. It comes with the terrain when you shoot wide-open. No amount of AF adjustment will alter the optical formula of the lens.

IMHO, shooting portraits wide open is never a good idea. You always risk getting the nose in focus but having the eyes out of focus, etc. And for an image of several partying people, 1/80 is a tad slow too. Even though the flash may freeze movement, where there is still some ambient light in a scene, subject and camera motion could still be recorded.
09-01-2012, 04:18 PM   #10
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QuoteOriginally posted by treebeard Quote
I guess I have to remember the shallow DOF along with having SR off (I think I read it should be off?)
This should have nothing to do with SR. If you had the camera on a tripod then SR should be off, if hand held then it should be on in that situation, I assume fairly dark from the high ISO.

The shallow DOF is your issue here, with that lens, at 4 foot distance and f/2.4 you only have 4.5" of in focus area. Think of it as a 4.5" thick box four feet in front of you. Anything inside the box is 'in focus' anything outside the box is 'out of focus'. Now think of the box as connected to your camera sensor and precisely in line with it, just four feet away. If your sensor is even slightly at an angle to your target the box will also be at an angle and pass through the target at that angle rather than including all of it. And if your target, in this case the girls faces, has a distance front to back of more than 4.5" then it is not possible to get all of it in focus.

QuoteOriginally posted by treebeard Quote
I am expecting more from the lens than I should be.
I disagree, the lens is doing exactly what you told it to do. If you want to make that shot, you need more DOF, which means a smaller aperture, maybe f/6.7 or f/8. Of course that means even higher ISO to get enough light in that situation. You could also get the subjects to 'pose' more precisely but for quick shots that is not always possible.

Sorry if you knew all that not trying to lecture.
09-01-2012, 04:29 PM   #11
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QuoteOriginally posted by jatrax Quote
This should have nothing to do with SR. If you had the camera on a tripod then SR should be off, if hand held then it should be on in that situation, I assume fairly dark from the high ISO.

The shallow DOF is your issue here, with that lens, at 4 foot distance and f/2.4 you only have 4.5" of in focus area. Think of it as a 4.5" thick box four feet in front of you. Anything inside the box is 'in focus' anything outside the box is 'out of focus'. Now think of the box as connected to your camera sensor and precisely in line with it, just four feet away. If your sensor is even slightly at an angle to your target the box will also be at an angle and pass through the target at that angle rather than including all of it. And if your target, in this case the girls faces, has a distance front to back of more than 4.5" then it is not possible to get all of it in focus.


I disagree, the lens is doing exactly what you told it to do. If you want to make that shot, you need more DOF, which means a smaller aperture, maybe f/6.7 or f/8. Of course that means even higher ISO to get enough light in that situation. You could also get the subjects to 'pose' more precisely but for quick shots that is not always possible.

Sorry if you knew all that not trying to lecture.
I believe I understand exactly what you are referring to. I shoot in poorly light clubs, dance places, bars, etc. Last night was one of the most poorly light places I have ever been. Here is another shot using the same lens, but 2 people and it came out much better, but again it was 2 people. I guess I should take these suggestions into consideration before I start messing with the AF adjustment for this particular lens. See image below. After looking at some of my images it might also appear that because it's soooooooooooo dark where I shoot I might THINK the AF has locked on but it might have locked on off of the target I was shooting for, which could easily explain the OOF people in the image.

Last edited by treebeard; 05-09-2013 at 04:24 PM.
09-02-2012, 07:26 AM   #12
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I went out last night and had to cover another event in almost complete darkness. I decided to bump up the ISO and shoot my 35/2.4 at f/4 using M mode. I underexposed my shots on purpose and My shots came out much better. I did not have any OOF shots.
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