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Archive 2012 · Is MFA only for AF calibration only?
  
 
RogerC11
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p.1 #1 · p.1 #1 · Is MFA only for AF calibration only?


Sometimes when the camera gives you focus confirmation light, the subject will either be backfocused or frontfocused which is what MFA is there for as I understand it. But if you are going by MF only and assuming you are focused by checking live view 10x also, would it still be possible for the image to be focused prior to taking the shot and still be misfocused after tripping the shutter? So is MFA only for the AF side aspect of focusing?


Sep 30, 2012 at 09:50 PM
Ian.Dobinson
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p.1 #2 · p.1 #2 · Is MFA only for AF calibration only?


No . MA only works with the phase detect system . Live view is reading from the image sensor.

If things are different on the live view screen to the actual image then either focus is changing in the time that the shutter trips . Or there is some focus shift going on as the lens stops down (assuming the lens is not shooting wide open) .



Sep 30, 2012 at 09:56 PM
RogerC11
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p.1 #3 · p.1 #3 · Is MFA only for AF calibration only?


So MF "should" give you more accurate focus every time regardless of what the confirmation light gives you (using live view 10x and competent photographer) as compared to the AF phase detect...correct?


Sep 30, 2012 at 10:05 PM
jcolwell
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p.1 #4 · p.1 #4 · Is MFA only for AF calibration only?


Using manual focus with image magnification in LiveView on a stationary camera should give accurate critical focus on a stationary subject. Autofocus might be just as good in the same situauion. Autofocus will often be better for moving subjects and moving cameras. AFAIK, the focus confirmation light lets you know that the image is within the current depth-of-field. That's not the same as achieving critical focus.

I don't know what you mean by MFA. If you're talking about AF microadjustment (AFMA)*, then yes, it's only for AF operation - it's a whole-system calibration technique.

* RTFM



Sep 30, 2012 at 10:33 PM
dwweiche
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p.1 #5 · p.1 #5 · Is MFA only for AF calibration only?


RogerC11 wrote:
So MF "should" give you more accurate focus every time regardless of what the confirmation light gives you (using live view 10x and competent photographer) as compared to the AF phase detect...correct?


You may be enlightened by reading the Lensrentals.com series on phase detect vs. contrast detect accuracy. Informative graphs make the difference easy to see.



Sep 30, 2012 at 10:42 PM
Ernie Aubert
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p.1 #6 · p.1 #6 · Is MFA only for AF calibration only?


You're confused by having read someone else's garbled acronym. What is "MFA"? Canon doesn't employ any "Micro Focus Adjustment" term. What you're asking about is "Auto Focus Micro Adjustment"; by definition, it relates to auto focus, with no bearing on manual focus.


Sep 30, 2012 at 10:42 PM
 

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Wahoowa
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p.1 #7 · p.1 #7 · Is MFA only for AF calibration only?


This reminds me of a question I got not too long ago while I was listing a Zeiss lens on B&S forum. the question was whether the lens had any front/back focus issue.


Sep 30, 2012 at 10:51 PM
Ferrophot
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p.1 #8 · p.1 #8 · Is MFA only for AF calibration only?


On my 7D once the lens/camera has been calibrated using AFMA AF seems to be more accurate than trying to MF through the viewfinder. Are these MF 50mms only for the FF boys and girls? Maybe I need some eye crutches.


Sep 30, 2012 at 11:53 PM
RogerC11
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p.1 #9 · p.1 #9 · Is MFA only for AF calibration only?


Yes, autofocus micro adjustment is what I meant. Thanks.


Sep 30, 2012 at 11:56 PM
Kenneth Farver
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p.1 #10 · p.1 #10 · Is MFA only for AF calibration only?


I'm thinking that if you are focusing using live view at 10X and your images are out of focus, that maybe the focusing screen of the camera needs to be shimmed like the ALT boys do when they change focusing screens. Just my uneducated guess.


Oct 01, 2012 at 12:04 AM
dwweiche
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p.1 #11 · p.1 #11 · Is MFA only for AF calibration only?


Kenneth Farver wrote:
I'm thinking that if you are focusing using live view at 10X and your images are out of focus, that maybe the focusing screen of the camera needs to be shimmed like the ALT boys do when they change focusing screens. Just my uneducated guess.


This would be possible if you were manually focusing through the viewfinder, but not with Live View.

Doby hit upon the only two possibilities for LV issues.



Oct 01, 2012 at 12:18 AM
BrianO
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p.1 #12 · p.1 #12 · Is MFA only for AF calibration only?


Kenneth Farver wrote:
I'm thinking that if you are focusing using live view at 10X and your images are out of focus, that maybe the focusing screen of the camera needs to be shimmed...


Nope. When using Live View, the LCD is showing an image captured directly from the imaging sensor, and the mirror is swung up out of the light path. So, no mirror = no image on the focusing screen.

(If you were using a camera with a semi-transmissive mirror, like some Sony cameras, you could have a live LCD view and a viewfinder view at the same time, maybe, but not with current Canon DSLRs.)



Oct 01, 2012 at 12:50 AM





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