Question on AF points


Jul 3, 2010
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#1
Hi all,

My camera has 9 AF points and I believe some other cameras have more. However, I cannot appreciate the multiple AF points as most of the time the camera give me focus at the wrong places.

So end up, I set the camera such that it always use the 'centre' AF point and I will use that centre AF point to focus and then re-compose my picture.

Am I silly for not being able to appreciate the multiple AF points?

Your views please.

Thanks.
 

ahbian

Senior Member
May 23, 2006
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#2
When you said focus on the wrong places, do you mean you allow the camera to select the AF point, or you specify the AF point but still the focus is off in that area?
 

Jul 3, 2010
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#3
When you said focus on the wrong places, do you mean you allow the camera to select the AF point, or you specify the AF point but still the focus is off in that area?
Yes, I meant I allow the camera to auto select the AF point(s). And apparently I couldn't appreciate such auto feature, so nowadays, I always select the 'centre' one, focus, and then recompose.
 

ahbian

Senior Member
May 23, 2006
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#4
Yes, I meant I allow the camera to auto select the AF point(s). And apparently I couldn't appreciate such auto feature, so nowadays, I always select the 'centre' one, focus, and then recompose.
If you let the camera select, then there is less control on your part. It might tend to grab areas of "high contrast etc" which might not be your intended subject of focus.

Choosing your own AF allows you more control, using centre AF and recompose usually works if your DOF is not too little.

My preference is to compose your picture first, then choose the (off centre) AF that covers your intended subject. Look at the section under Manual AF point selection in the link below, the photo is what I meant.

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3049

This is one of the reasons why people like more AF points, sometimes it not for the purpose of using them all together in a single shot.
 

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Jul 3, 2010
42
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#5
If you let the camera select, then there is less control on your part. It might tend to grab areas of "high contrast etc" which might not be your intended subject of focus.

Choosing your own AF allows you more control, using centre AF and recompose usually works if your DOF is not too little.

My preference is to compose your picture first, then choose the (off centre) AF that covers your intended subject. Look at the section under Manual AF point selection in the link below, the photo is what I meant.

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3049

This is one of the reasons why people like more AF points, sometimes it not for the purpose of using them all together in a single shot.
Thanks. The link is useful.

Your method of composing the picture first and then manually choose the AF points is slightly different from my 'usual' way of shooting but it's nonetheless a viable suggestion. I will give it a try and I think I need to exercise my thumb more and make it move quicker. :)
 

sinned79

Senior Member
Jun 18, 2009
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www.aboutlove.sg
#6
Hi all,

My camera has 9 AF points and I believe some other cameras have more. However, I cannot appreciate the multiple AF points as most of the time the camera give me focus at the wrong places.

So end up, I set the camera such that it always use the 'centre' AF point and I will use that centre AF point to focus and then re-compose my picture.

Am I silly for not being able to appreciate the multiple AF points?

Your views please.

Thanks.
u are not alone :bsmilie:

this is what i had been doing.

there is a problem with 5DMKII... only the center focusing is fast... so i usually only use center focusing. :)
 

GRbenji

New Member
May 24, 2010
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#7
Using the centre AF point to focus and recompose, subject will always be in front of focal plane.
 

Jul 3, 2010
42
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31
#8
u are not alone :bsmilie:

this is what i had been doing.

there is a problem with 5DMKII... only the center focusing is fast... so i usually only use center focusing. :)
Phew. Glad to know that I am not alone. :)
 

Jul 3, 2010
42
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#9
u are not alone :bsmilie:

this is what i had been doing.

there is a problem with 5DMKII... only the center focusing is fast... so i usually only use center focusing. :)
Using the centre AF point to focus and recompose, subject will always be in front of focal plane.
Thanks. I thought so too.
 

torak

New Member
Sep 4, 2009
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#11
Using the centre AF point to focus and recompose, subject will always be in front of focal plane.
If u r using a shallow dof (like 85mm f1.4), and u use center af to focus on eyes and recompose, ur subject's eyes will definitely be oof.
 

GRbenji

New Member
May 24, 2010
1,057
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#12
If u r using a shallow dof (like 85mm f1.4), and u use center af to focus on eyes and recompose, ur subject's eyes will definitely be oof.
Isn't that similar to what I've said? In front or behind focal plane means not in perfect focus. DOF affect how much it is oof.
 

ovaltinemilo

Senior Member
Sep 12, 2009
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Sin jia Po lah
#14
Hi all,

My camera has 9 AF points and I believe some other cameras have more. However, I cannot appreciate the multiple AF points as most of the time the camera give me focus at the wrong places.

So end up, I set the camera such that it always use the 'centre' AF point and I will use that centre AF point to focus and then re-compose my picture.

Am I silly for not being able to appreciate the multiple AF points?

Your views please.

Thanks.
I think it's better to choose your own Af point. Most ppl use the centre AF point then recompose.

If you are using a lens that give very thin DOF, you will come to realise the usefulness when the usual center af + recompose will most prob give oof.
 

ahbian

Senior Member
May 23, 2006
2,467
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0
#15
Read this.

However, the effect is minimal.
Thanks for sharing, quite a heavy read.

Still haven't gotten my head around how the numbers would work out for a lens with a much closer focusing distance. Less impact than the 10-22mm?

I do think most of the time the technique of centre AF and recompose would give acceptable results, if not can fine tune by selecting AF points. For me, the scrolling through of AF points is quite instinctive already. :)
 

Numnumball

Senior Member
Mar 6, 2009
13,899
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Central
#16
If u r using a shallow dof (like 85mm f1.4), and u use center af to focus on eyes and recompose, ur subject's eyes will definitely be oof.
D700/85f1.4 user here.. I choose muliple af points and focus at hyperfocal distance (norm a point in between both eyes), no prob.. Mayb u can try n do the same. :)

of cos other factors like position of ur subject parallel to ur focal plane will mote or less eliminate the above prob..
 

Reportage

Senior Member
Nov 24, 2008
5,785
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#17
depends what you do.

for sports, i select my AF points manually. some cameras when you use the centre AF point will suddenly become more quicker.
 

heshanj

New Member
Aug 18, 2009
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Ho Chi Minh City
pixelogist.me
#18
from wat i've read, the focusing and recomposing generally works fine - its not very noticeable unless in extreme conditions, like mentioned above, such as very shallow DOF. however, if i can use an AF point that is suited to my composition, i generally manually select it, to avoid any chance of getting a slightly out of focus image.. if not, i focus and recompose
 

Jan 3, 2008
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SG
#19
I also having the same problem.

1. Center is fast but when you are shooting portraits, face of the subject may be OOF if DPF is swallow (torso sharp but not face).
2. Manually adjust AF point can be slow (lag by >3 sec). By the time you select your previous desirable AF point, the subject has long shifted his/her position. Definitely not recommended for SPORTS.

I'm a Canon user as you can see. Is Nikkon matrix AF system works better? Like to listen to some of the 1D, 7D and Nikkon users comment.
 

Octarine

Moderator
Staff member
Jan 3, 2008
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Pasir Ris
#20
2. Manually adjust AF point can be slow (lag by >3 sec). By the time you select your previous desirable AF point, the subject has long shifted his/her position. Definitely not recommended for SPORTS.
I use one CFn where you can put the AF point selection at the arrow keys, center button is center AF point. Works pretty well and is faster than 3s, not even looking when used to it.
I'm a Canon user as you can see. Is Nikkon matrix AF system works better? Like to listen to some of the 1D, 7D and Nikkon users comment.
Are you sure this exists? Matrix Metering system is also used in Canon bodies, they just name it differently.
 

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