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02-20-2016, 10:48 PM   #1
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How do you fine-tune Autofocus?

Hey all.

While testing some various lenses this evening, I noticed that all of them seem to be consistently out of focus (ever so slightly) on my K-50, enough that 100% crops at 100 ISO are being affected in clarity. I know there is an autofocus fine tune setting in the camera, but I can't seem to discern any difference between the individual steps of the fine tuning. How am I supposed to narrow down the fine tune settings so I know exactly which one to use? I can't tell the difference between +6 and +7, for example, but I can see a clear difference between 0 and +5. The result is I know the general direction I need to tune the setting, but I don't know where to stop. Is there some sort of method I can use to see minute details of how in-focus something is?

02-20-2016, 10:57 PM   #2
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If you get one of these test setups, you'll have a much easier time adjusting different lenses:
Fixing Front and Back Focus - Introduction - In-Depth Articles

Also, are you sure the softness you're seeing is related to AF and not some other factor (such as the lens itself, diffraction, etc.)?

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02-20-2016, 11:02 PM   #3
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QuoteOriginally posted by fullmental Quote
Hey all.

While testing some various lenses this evening, I noticed that all of them seem to be consistently out of focus (ever so slightly) on my K-50, enough that 100% crops at 100 ISO are being affected in clarity. I know there is an autofocus fine tune setting in the camera, but I can't seem to discern any difference between the individual steps of the fine tuning. How am I supposed to narrow down the fine tune settings so I know exactly which one to use? I can't tell the difference between +6 and +7, for example, but I can see a clear difference between 0 and +5. The result is I know the general direction I need to tune the setting, but I don't know where to stop. Is there some sort of method I can use to see minute details of how in-focus something is?
From what you are saying, it appears as though you need to turn this over to a technician. Even though the +6 and +7 are close, you should be able to see even a slight difference. I seem to recall another member having this same issue with the k-50. Well, good luck. I would like to know what the end result will be.

Rgds,

Tony
02-20-2016, 11:02 PM   #4
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QuoteOriginally posted by Adam Quote
If you get one of these test setups, you'll have a much easier time adjusting different lenses:
Fixing Front and Back Focus - Introduction - In-Depth Articles

Also, are you sure the softness you're seeing is related to AF and not some other factor (such as the lens itself, diffraction, etc.)?
Thank you for the link, I'll look into that.

As for the softness, I'm taking multiple photos with the same lens in the same position, lighting, settings, and object and seeing a difference with consistent results based on the AF setting. The only thing that I'm changing is the AF fine tune setting (or a very meticulous manual focus as a baseline). I do believe that rules out the other factors you listed?

---------- Post added 02-20-16 at 11:39 PM ----------

Hmm, okay so I took a look at the article linked. I don't have any fancy calibration cards around but I did have a ruler that is accurate to 1/32", so I laid that at about a 40 degree angle and focused on the center line to test. The result was that two of my lenses have back-focusing issues that cannot be compensated for (they hit +10 and it's still not in focus), one is perfect as-is, and one of them front focuses to the point I can't compensate for it either (-10, still not centered, but it does come close). Does that sound like lens issues or a camera issue to you? The lenses are all older and out of warranty, but the camera isn't.


Last edited by fullmental; 02-20-2016 at 11:42 PM.
02-21-2016, 12:16 AM   #5
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Wait, no I see what's happening. I'm not actually saving the adjustments, On most of the adjustments I was pressing "menu" to get out of the screen, and that's actually the cancel button. The few times it seemed to work I was probably using the OK button like I'm supposed to .

I stopped being stupid and cancelling the adjustments, now I can get decent results after all. Looks like my four lenses are -3, 0, +5, and +8. That makes me think that it's just the various lenses needing adjustment, not the camera itself. I suppose it shouldn't surprise me, every single lens I have other than my 50-200mm WR (the +0 lens) are older and have gone through several owners, and the +8 lens (my 80-320mm) is the oldest, worst-focusing, and worst-condition lens in general that I have.
02-21-2016, 07:14 AM   #6
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I don't think the age of the lens has anything to with it. It's just the camera/lens combination. One lens of mine is -8 on my K-5 and +5 on my K-5 II. All of my lenses were purchased new.

An afterthought: Although all my lenses were purchased new and tested soon after purchase (at least on the K-5), the individual camera/lens adjustment could change with usage and time. I have not, however, tested out that theory.

Last edited by cpk; 02-21-2016 at 07:51 AM.
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