Can't get AF-C to work?


Exhaust

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Dec 11, 2010
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#1
Hi peeps, i have been trying out the AF-C mode today. After i focused on my subject and kept the half shutter on, as my subject moves i can hear my lens refocusing but when the shot and reviewed my picture it was outta focus. My subject was not moving fast as well.. how come?
 

kei1309

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Apr 12, 2010
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#2
what AF area are you on? if you're in multi, what you're gonna get is a hit-and-miss focusing lock. lemme guess. somewhere in the middle... the background?
 

tskeng

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Jul 16, 2009
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#3
what AF area are you on? if you're in multi, what you're gonna get is a hit-and-miss focusing lock. lemme guess. somewhere in the middle... the background?
Any tips on how to use AF-C?
 

TWmilkteaTW

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May 30, 2011
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#4
im on AF multi too.. sometimes i got frustrated too. Specially when i want to get my focus on the eyes.. the AF point just wont go there. ( NEX user ) anyone can enlighten me?
 

rhino123

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#5
I have not use a Sony long enough but if I was to guess, it might be your lens too. Some lens don't focus fast enough.
 

kei1309

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#7
if you're multi-AF, the camera will just focus on the most prominent subject.

in the case of lower-end cameras, they have cross-type sensors at the center. what does that mean? it means that the focusing is more accurate at the center as it's more sensitive.

if you use multi-AF, the cross-type sensors are more sensitive and when the subject moves away from the middle towards the less sensitive AF points, the camera will instead lock the focus using the cross types. especially if the background is contrasty and prominent.
 

rhino123

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#8
if you're multi-AF, the camera will just focus on the most prominent subject.

in the case of lower-end cameras, they have cross-type sensors at the center. what does that mean? it means that the focusing is more accurate at the center as it's more sensitive.

if you use multi-AF, the cross-type sensors are more sensitive and when the subject moves away from the middle towards the less sensitive AF points, the camera will instead lock the focus using the cross types. especially if the background is contrasty and prominent.
Lets see if I get it right... so lets say if your background is a white sheet of paper or your subject (say a slow moving bug) is on a white piece of paper and so when I am on Multi-AF, and the bug moved away from the middle AF point (although cross type), but since there is nothing there to focus on, the camera other focus points will take over and trace that bug.

Am I right?
 

Exhaust

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Dec 11, 2010
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#9
what AF area are you on? if you're in multi, what you're gonna get is a hit-and-miss focusing lock. lemme guess. somewhere in the middle... the background?
I used AF-C with Dynamic Area Focus. So i focused the blinking red spot (AF) on my subject and kept my camera steady while he moved. But i do not seem to see AF-C or the Dynamic Area Focus to work.
 

kei1309

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#10
Lets see if I get it right... so lets say if your background is a white sheet of paper or your subject (say a slow moving bug) is on a white piece of paper and so when I am on Multi-AF, and the bug moved away from the middle AF point (although cross type), but since there is nothing there to focus on, the camera other focus points will take over and trace that bug.

Am I right?
yea. it works like that.
 

kei1309

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#11
I used AF-C with Dynamic Area Focus. So i focused the blinking red spot (AF) on my subject and kept my camera steady while he moved. But i do not seem to see AF-C or the Dynamic Area Focus to work.
sorry i'm not a nikon user so i'm not too sure what's dynamic area focus. what is the AF readout area when you're using that?
 

Exhaust

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Dec 11, 2010
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#12
sorry i'm not a nikon user so i'm not too sure what's dynamic area focus. what is the AF readout area when you're using that?
It is supposed to track moving objects which kinda work hand in hand with AF-C just now i dun 'see' it happening.
 

kei1309

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#13
It is supposed to track moving objects which kinda work hand in hand with AF-C just now i dun 'see' it happening.
ok try another test. get your subject to walk towards the camera from back to front. see whether the image gets sharper. you should see something like this:

[video=youtube;kHPaVD0pHpQ]http://www.youtube.com/watch?v=kHPaVD0pHpQ[/video]

notice from far, everything is sharp. if your AF-C works, you should get the background blurred as the subject gets closer.
 

Exhaust

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Dec 11, 2010
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#14
ok try another test. get your subject to walk towards the camera from back to front. see whether the image gets sharper. you should see something like this:

[video=youtube;kHPaVD0pHpQ]http://www.youtube.com/watch?v=kHPaVD0pHpQ[/video]

notice from far, everything is sharp. if your AF-C works, you should get the background blurred as the subject gets closer.
Ok thanks! will try it out after work later =)

Btw.. do you guys get to use this function often?
 

rhino123

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#15
Ok thanks! will try it out after work later =)

Btw.. do you guys get to use this function often?
Actually I have never use this function or its equivalent for my Canon 7D before. I just doesn't seemed to know how to control it... maybe I am too much an oldtimer ;)
 

Exhaust

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#16
Actually I have never use this function or its equivalent for my Canon 7D before. I just doesn't seemed to know how to control it... maybe I am too much an oldtimer ;)
Haha i thought of using it because i was thinking if i wanna capture small kids playing at the playground stuff like that, would it be better to use these AF-C + Dynamic Area Focus function? Cause if i were to just use AF-S with single spot focus, and my shutterspeed is not fast enough due to the low ambient light, i must therefore upen up my aperture to maybe f2.8? so it may not be easy to capture a sharp image if i were to lock in the focus and the kid happens to move out of my focal plane.
 

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