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Author Topic: 24L II Lens Focusing Issue  (Read 1223 times)

jwong

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24L II Lens Focusing Issue
« on: March 04, 2012, 04:37:42 PM »
Purchased a lens with UZ date code from Ebay and found that the phase-detect focus is not accurate (using center point on 7D).  The focus tends to be behind the focus point and varies with object distance, so it is not consistent.  With Liveview, focus is accurate all the time.  Is this a case of a bad lens?

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24L II Lens Focusing Issue
« on: March 04, 2012, 04:37:42 PM »

neuroanatomist

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Re: 24L II Lens Focusing Issue
« Reply #1 on: March 04, 2012, 06:43:04 PM »
Sounds like a textbook case of why the 7D features AF Microadjustment.

Here are my AFMA tips, you might also check out the Reikan FoCal software (which I currently use).
EOS 1D X, EOS M, and lots of lenses
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jwong

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Re: 24L II Lens Focusing Issue
« Reply #2 on: March 04, 2012, 07:42:21 PM »
Sounds like a textbook case of why the 7D features AF Microadjustment.

Here are my AFMA tips, you might also check out the Reikan FoCal software (which I currently use).

I tried using focus adjustment to the limit (+20) but it did not fix the issue for all distances.  The correction was about +17 at around 3 ft, +10 at around 6 ft.  I tried shooting at f/1.4, f/2, f/2.8, f/4, f/5.6 and f/8 with the center point and none of them are consistently sharp.  Is it fair to assume that it is an autofocus issue?

neuroanatomist

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Re: 24L II Lens Focusing Issue
« Reply #3 on: March 04, 2012, 08:11:22 PM »
I think so, but asssuming that Live View is accurate at all distances, the lens may need service.  It's normal for different adjustments to be needed at different distances - usually, at the MFD is different than most of the focal range.  I would guess that your camera and this lens are on opposite ends of the tolerance spectrum.
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jwong

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Re: 24L II Lens Focusing Issue
« Reply #4 on: March 04, 2012, 08:22:43 PM »
I think so, but asssuming that Live View is accurate at all distances, the lens may need service.  It's normal for different adjustments to be needed at different distances - usually, at the MFD is different than most of the focal range.  I would guess that your camera and this lens are on opposite ends of the tolerance spectrum.

Thanks for responses.  Yes, Live View did work at all tested distances.  It was shocking the difference between phase-detection and Live View and how consistently in-focus Live View was without manual override.  I'm now trying to get the purchase documentation from the Ebay seller (it's less than a year old), and if that doesn't work, I guess I'll find out how good Ebay's buyer protection program is.

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Re: 24L II Lens Focusing Issue
« Reply #4 on: March 04, 2012, 08:22:43 PM »