Canon 7D
Why does the Live View autofocus always hit the focus better every time than autofocus through the ViewFinder?
chuckmiller Goldmember  More info | Sep 05, 2012 21:58 | #1 Canon 7D .
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gjl711 Wait.. you can't unkill your own kill.  57,738 posts Likes: 4072 Joined Aug 2006 Location: Deep in the heart of Texas More info | Sep 05, 2012 22:02 | #2 Simple. Live view uses the image sensor to do focusing. The light that is focused takes the same path as what will illuminate the image sensor. The VF uses a different light path. The light is intercepted and diverted to the VF. Any difference between the length of these light paths will mean that the image will be OOF. Not sure why, but call me JJ.
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Sep 05, 2012 22:05 | #3 gjl711 wrote in post #14953287  ...However, if the difference is minimal, you can use MFA to adjust the AF so that they will be the same. The 7D supports MFA so you might want to try that. I was wondering if MFA influences both or just VF autofocus. Since LiveView lifts the mirror I guess there in is the answer. .
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gjl711 Wait.. you can't unkill your own kill. 57,738 posts Likes: 4072 Joined Aug 2006 Location: Deep in the heart of Texas More info | Sep 05, 2012 22:20 | #4 chuckmiller wrote in post #14953307 I was wondering if MFA influences both or just VF autofocus. Since LiveView lifts the mirror I guess there in is the answer. LV focus uses a different technique not the phase detect of the normal VF focusing. So, it focuses until the image shows maximum contrast. The advantage is more accurate focus but much slower. Not sure why, but call me JJ.
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Sep 06, 2012 04:27 | #5 The phase detect of the VF focusing works a bit like this...
If the camera slightly miscalculates the amount of movement required, or the lens doesn't move the correct distance then the focusing will be off slightly. As it is impossible to manufacture anything to infinite precision there will always be some slight errors, resulting in slight (often unnoticeable) error in focus. MFA is designed to partially correct this. The contrast detect method of the LV focusing works more like this...
Frank Hollis - Retired mass spectroscopist
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stsva Cream of the Crop  More info | Sep 06, 2012 07:26 | #6 hollis_f wrote in post #14954205 The phase detect of the VF focusing works a bit like this...
The contrast detect method of the LV focusing works more like this...
You scientific types are always so technical about everything! Some Canon stuff and a little bit of Yongnuo.
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gjl711 Wait.. you can't unkill your own kill. 57,738 posts Likes: 4072 Joined Aug 2006 Location: Deep in the heart of Texas More info | Sep 06, 2012 08:00 | #7 Frank, I love your explanation. Not sure why, but call me JJ.
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TeamSpeed 01010100 01010011  More info | Sep 06, 2012 09:00 | #8 I don't know, I think this was a great way to explain it in a non-technical format. Past Equipment | My Personal Gallery
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Hermeto Cream of the Crop  6,674 posts Likes: 2 Joined Oct 2005 Location: Toronto, Canada More info | Sep 06, 2012 09:16 | #9  Permanent banTeamSpeed wrote in post #14954841 I don't know, I think this was a great way to explain it in a non-technical format.  “Everything should be as simple as it can be, but not simpler.” What we see depends mainly on what we look for.
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joeblack2022 Goldmember 3,005 posts Likes: 5 Joined Sep 2011 Location: The Great White North More info | Sep 06, 2012 09:21 | #10 LOL at Frank's explanation! Joel
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