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Author Topic: Camera back-focuses. MA not the issue!  (Read 3947 times)

KHAS

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Camera back-focuses. MA not the issue!
« on: March 26, 2012, 02:10:30 PM »
So, I've been having this problem for a while now, whereby when I shoot portraits and focus on the eye, in the resulting image the eyes are soft but the ear is pin-sharp! Have had it with the 70-200 2.8 mkII, 24-105 L, the 85 L 1.2 and the 50 1.4 (all canon) on a 1D mkIV. I figured it was a simple AFMA soution, but after doing multiple tests here, the only lens which needed any calibration was my 16-35mm 2.8 (which I don't even use for portraits). Any ideas on why I am getting this issue if the tests are showing up sharp images without any MA? P.s. I might shoot at 1.4 or f8, so it's not a result of just shooting wide open. Pulling my hair out here!  >:(

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Camera back-focuses. MA not the issue!
« on: March 26, 2012, 02:10:30 PM »

shizam1

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Re: Camera back-focuses. MA not the issue!
« Reply #1 on: March 26, 2012, 03:04:14 PM »
Well, it could be focus/recompose.  If you focus on center spot on the subjects eye, then move camera to recompose, focus will shift somewhat. But I think it would result in a front focus, not back in that scenario...

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Re: Camera back-focuses. MA not the issue!
« Reply #2 on: March 26, 2012, 03:10:55 PM »
focus/recompose using center spot on the eye, putting the eye on upper part of the frame in a vertical orientation would induce back focus. 

the plane of focus would shift backwards as you rotated the camera down, in a verical orientation.

just an example, but may not be how you're shooting.

i tend to get this with any lens longer than 100mm, or any apertures wider than 2.8, where i typically shift to MF in those cases
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drummstikk

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Re: Camera back-focuses. MA not the issue!
« Reply #3 on: March 26, 2012, 04:17:07 PM »
Help me be sure I understand exactly what the issue is here. There seems to be a contradiction when you say your images are consistently back-focused, yet the calibration for micro-adjust indicates no adjustment necessary.

When you say you "focus on the eye," are you doing this manually or with AF? Other posters are right when they say AF-ing with the center point and recomposing can lead to incorrect focus. I am constantly re-selecting a focus point manually on my 7D so the AF point is right on or as close as possible to the point in the image I want in focus. On the other hand, if you are critically focusing manually and getting consistently mis-focused images this may suggest something else.

Please advise.

As an aside, this may start a debate, but I think AF micro-adjust should only be used as a stopgap to get you by until you can get the camera and lens to a service center for repair/adjustment. It's kind of a blunt instrument and you may correct your focus errors close in, but then cause problems with focus on more distant objects, or vice versa.
"Focused. Or focused not. There is no 'almost.'"

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Mt Spokane Photography

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Re: Camera back-focuses. MA not the issue!
« Reply #4 on: March 26, 2012, 05:16:21 PM »
Please advise.

As an aside, this may start a debate, but I think AF micro-adjust should only be used as a stopgap to get you by until you can get the camera and lens to a service center for repair/adjustment. It's kind of a blunt instrument and you may correct your focus errors close in, but then cause problems with focus on more distant objects, or vice versa.

Unfortunately, no amount of factory adjustment of a wide aperture lens will have it focusing perfectly on all your bodies, there is just too fine of a requirement for perfect focus at f/1.2.
 
As long a camera / lens is close, a micro adjustment is all that is needed.  Even if I were to pay $3400 to have all 16 of my Canon lenses and both bodies adjusted to each other, as soon as my 5D MK III arrives again tomorrow, I'd have to do it all again.
 

KHAS

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Re: Camera back-focuses. MA not the issue!
« Reply #5 on: March 26, 2012, 07:16:33 PM »
I always shift the focus point to the area of the eye in order to avoid the recompose issue. I might just need to send everything to canon but since I shoot 6 days a week, it's pretty difficult to find the time unless I borrow some gear! Could there be any other factor I'm not considering?

KHAS

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Re: Camera back-focuses. MA not the issue!
« Reply #6 on: March 26, 2012, 07:21:46 PM »
Help me be sure I understand exactly what the issue is here. There seems to be a contradiction when you say your images are consistently back-focused, yet the calibration for micro-adjust indicates no adjustment necessary.

When you say you "focus on the eye," are you doing this manually or with AF? Other posters are right when they say AF-ing with the center point and recomposing can lead to incorrect focus. I am constantly re-selecting a focus point manually on my 7D so the AF point is right on or as close as possible to the point in the image I want in focus. On the other hand, if you are critically focusing manually and getting consistently mis-focused images this may suggest something else.

Please advise.

I'm using AF for focus rather than MF

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Re: Camera back-focuses. MA not the issue!
« Reply #6 on: March 26, 2012, 07:21:46 PM »

neuroanatomist

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Re: Camera back-focuses. MA not the issue!
« Reply #7 on: March 28, 2012, 02:29:52 PM »
... but after doing multiple tests here, the only lens which needed any calibration was my 16-35mm 2.8 (which I don't even use for portraits). Any ideas on why I am getting this issue if the tests are showing up sharp images without any MA?

What sort of tests?
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Mt Spokane Photography

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Re: Camera back-focuses. MA not the issue!
« Reply #8 on: March 28, 2012, 04:30:23 PM »
You might describe your testing as to how it was done, what settings, distance, etc.  The other thing to consider is that a camera will not be 100 percent repeatable, so you must take multipoe shots at each setting, resetting the lens to infinity each time before focusing.  Its very tedious and a painstaking job to find out what AFMA to use.
 
And, of course, the camera can have a intermittent issue.

KHAS

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Re: Camera back-focuses. MA not the issue!
« Reply #9 on: March 29, 2012, 08:11:25 AM »
Sorry for the delayed response! The test I was using was the same one described here: http://arihazeghiphotography.com/MA-web/

I did multiple exposures to check for inconsistencies. I didn't set the lens to infinity each time so that might have skewered my results! As advised, I set the lens 20x the distance away from the target depending on focal length. But due to the area I was working in, I couldn't test my 70-200mm 2.8 II at the 200mm focal length, which I'd have liked to do. Reluctant to send the my 1DmkIV + 5DmkII back to Canon, as I will be replacing them with 2 5DmkIII's very shortly.
On a side note, Has anyone tested the new 5D against the 1DmkIV, with regards to high ISO and AF?

neuroanatomist

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Re: Camera back-focuses. MA not the issue!
« Reply #10 on: March 29, 2012, 11:42:46 AM »
Sorry for the delayed response! The test I was using was the same one described here: http://arihazeghiphotography.com/MA-web/

First time I've run across that method.  I am not convinced it's correct, specifically, "Each click on the ( > ) or ( < ) corresponds to one unit in the AF micro adjust scale in the camera."  Each AFMA unit corresponds to 1/8 of the depth of focus, but I'm not sure that equals one focus step in tethered focusing.
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Kahuna

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Re: Camera back-focuses. MA not the issue!
« Reply #11 on: March 29, 2012, 12:35:51 PM »
Sorry for the delayed response! The test I was using was the same one described here: http://arihazeghiphotography.com/MA-web/

First time I've run across that method.  I am not convinced it's correct, specifically, "Each click on the ( > ) or ( < ) corresponds to one unit in the AF micro adjust scale in the camera."  Each AFMA unit corresponds to 1/8 of the depth of focus, but I'm not sure that equals one focus step in tethered focusing.

I played with the method above on my 100mm f/2.8 and 85mm f/1.2 II.  Reikan had the 100mm at +0 and the 85 at -3.  Method mentioned above didn't change the 100mm but changed the 85 to +10.  very poor results with test shot.  Reikan is far more accurate.

KHAS

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Re: Camera back-focuses. MA not the issue!
« Reply #12 on: March 30, 2012, 09:21:33 AM »
@Kahuna, thanks for the reply. Do you have a link or something to the Reikan method? might be worth giving it a try to see if the results are different.

@Neuro, I only came across it based on another CanonRumours members experience. I don't have anything to compare it to, so not sure how accurate it is. I also agree that no piece of equipment is always 100% reliable and consistent, and not to bother chasing THAT magical rainbow!  :D
I heard someone mention switching to spot AF helped their cause, so I might try that and see if it helps. Again, I appreciate all the responses.

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Re: Camera back-focuses. MA not the issue!
« Reply #12 on: March 30, 2012, 09:21:33 AM »

neuroanatomist

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Re: Camera back-focuses. MA not the issue!
« Reply #13 on: March 30, 2012, 09:39:38 AM »
@Kahuna, thanks for the reply. Do you have a link or something to the Reikan method? might be worth giving it a try to see if the results are different.
http://www.reikan.co.uk/focal/
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Mt Spokane Photography

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Re: Camera back-focuses. MA not the issue!
« Reply #14 on: March 30, 2012, 01:09:14 PM »
Sorry for the delayed response! The test I was using was the same one described here: http://arihazeghiphotography.com/MA-web/

I did multiple exposures to check for inconsistencies. I didn't set the lens to infinity each time so that might have skewered my results! As advised, I set the lens 20x the distance away from the target depending on focal length. But due to the area I was working in, I couldn't test my 70-200mm 2.8 II at the 200mm focal length, which I'd have liked to do. Reluctant to send the my 1DmkIV + 5DmkII back to Canon, as I will be replacing them with 2 5DmkIII's very shortly.
On a side note, Has anyone tested the new 5D against the 1DmkIV, with regards to high ISO and AF?

Try this site.  http://regex.info/blog/photo-tech/focus-chart
 
Canon has mentioned 50X the focal length as the ideal distance, however you can AFMA at any distance.  The thing to remember is that if you AFMA at close distances, you are likely to experience back focus at longer distances, and the converse.
 
 

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Re: Camera back-focuses. MA not the issue!
« Reply #14 on: March 30, 2012, 01:09:14 PM »