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Are many autofocus points nessesary??



 
 
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  #1  
Old April 28th 07, 11:17 AM posted to rec.photo.digital
Soren
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Posts: 11
Default Are many autofocus points nessesary??

Hi,

I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..

Any clearafication is appreciated

Soren

  #2  
Old April 28th 07, 12:59 PM posted to rec.photo.digital
Rutger
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Posts: 98
Default Are many autofocus points nessesary??

"Soren" schreef in bericht
oups.com...
Hi,

I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..


I always use just the middle point, and when i want to focus on something
that's not in the middle i focus on it and change the position after that,
holding the shutter-release half pressed. maybe oldfashioned, but works
easiest.
Note that you have to use the appropiate setting: hence no servo-focussing.

Rutger


--
http://www.flickr.com/photos/zwaarddrager


  #3  
Old April 28th 07, 01:21 PM posted to rec.photo.digital
Roy G
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Posts: 878
Default Are many autofocus points nessesary??


"Soren" wrote in message
oups.com...
Hi,

I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..

Any clearafication is appreciated

Soren


Yes.

5, 7, 9, 11 point focussing is all part of the sales spiel for the techno
buyers who must have the highest spec. Of even less importance than the ever
increasing number of pixels.

If you know what you are doing, 1 focus point is all you need. I would
advocate only ever using 1 at a time, but it is sometimes convenient to
select an off centre point, so there is some justification for having more
than 1.

Roy G


  #4  
Old April 28th 07, 01:33 PM posted to rec.photo.digital
Roger N. Clark (change username to rnclark)
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Posts: 1,818
Default Are many autofocus points nessesary??

Rutger wrote:
"Soren" schreef in bericht
oups.com...
Hi,

I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..


I always use just the middle point, and when i want to focus on something
that's not in the middle i focus on it and change the position after that,
holding the shutter-release half pressed. maybe oldfashioned, but works
easiest.
Note that you have to use the appropiate setting: hence no servo-focussing.

Rutger


Many focus points are needed to be able to compose freely and have
the focal point where you want it. For example, when imaging wildlife
or people, a key to a great photo is focusing on the eyes.
Here is an example:

http://www.clarkvision.com/galleries...0240b-700.html

I used manual focus point selection, and AI servo. The AI servo tracks
focus as the subject moves toward or away from the camera, and even predicts
the rate of change and moves the focus to the predicted point when
the shutter actually fires, as opposed to when you press the button,
thus compensating for the shutter lag. If you just use center focus
all the time, focus would not be on the eyes, for example, in this shot:

http://www.clarkvision.com/galleries...8463b-700.html

During action, as I follow the action, I manually move the focus
point to keep an AF sensor on the eyes while maintaining the
composition I want. I use a 1D Mark II which has 45 AF points.
I wish it had more AF points!

Roger
  #5  
Old April 28th 07, 01:43 PM posted to rec.photo.digital
bluezfolk
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Posts: 69
Default Are many autofocus points nessesary??

On Apr 28, 6:59 am, "Rutger" wrote:
"Soren" schreef in ooglegroups.com...

Hi,


I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..


I always use just the middle point, and when i want to focus on something
that's not in the middle i focus on it and change the position after that,
holding the shutter-release half pressed. maybe oldfashioned, but works
easiest.
Note that you have to use the appropiate setting: hence no servo-focussing.

Rutger

--http://www.flickr.com/photos/zwaarddrager


I agree with Rutger, and find that its easier to do it that way than
to select which focus point I want to use.


Eric

  #6  
Old April 28th 07, 02:57 PM posted to rec.photo.digital
Soren
external usenet poster
 
Posts: 11
Default Are many autofocus points nessesary??

On Apr 28, 2:33 pm, "Roger N. Clark (change username to rnclark)"
wrote:
Rutger wrote:
"Soren" schreef in bericht
roups.com...
Hi,


I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..


I always use just the middle point, and when i want to focus on something
that's not in the middle i focus on it and change the position after that,
holding the shutter-release half pressed. maybe oldfashioned, but works
easiest.
Note that you have to use the appropiate setting: hence no servo-focussing.


Rutger


Many focus points are needed to be able to compose freely and have
the focal point where you want it. For example, when imaging wildlife
or people, a key to a great photo is focusing on the eyes.
Here is an example:

http://www.clarkvision.com/galleries.../lion.c01.23.2...

I used manual focus point selection, and AI servo. The AI servo tracks
focus as the subject moves toward or away from the camera, and even predicts
the rate of change and moves the focus to the predicted point when
the shutter actually fires, as opposed to when you press the button,
thus compensating for the shutter lag. If you just use center focus
all the time, focus would not be on the eyes, for example, in this shot:

http://www.clarkvision.com/galleries.../lion.c01.20.2...

During action, as I follow the action, I manually move the focus
point to keep an AF sensor on the eyes while maintaining the
composition I want. I use a 1D Mark II which has 45 AF points.
I wish it had more AF points!

Roger


Thanks for all the answers everyone! So multiple AF points is really
good if you use the servo and track a motion and want to maintain a
certain composition. But for still photos I can use the center point
and move the camera (as I do now) without getting into trouble.

Thanks for the nice examples Roger, great pictures by the way!

Soren

  #7  
Old April 28th 07, 04:08 PM posted to rec.photo.digital
Paul Repacholi
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Posts: 45
Default Are many autofocus points nessesary??

Soren writes:

certain composition. But for still photos I can use the center point
and move the camera (as I do now) without getting into trouble.


Canon have recomended against this, and have said that for best AF
accuracy you should NOT focus and re-frame, but to use the AF point
in the best position.
  #8  
Old April 28th 07, 05:30 PM posted to rec.photo.digital
Randall Ainsworth
external usenet poster
 
Posts: 559
Default Are many autofocus points nessesary??

In article , Paul Repacholi
wrote:

Canon have recomended against this, and have said that for best AF
accuracy you should NOT focus and re-frame, but to use the AF point
in the best position.


They're full of ****.
  #9  
Old April 28th 07, 07:41 PM posted to rec.photo.digital
Westy
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Posts: 15
Default Are many autofocus points nessesary??

On Sat, 28 Apr 2007 12:21:00 GMT, "Roy G"
wrote:


"Soren" wrote in message
roups.com...
Hi,

I was wondering, what is the advantage of many autofocus points? When
I use autofocus on my 400D I sometimes have to hunt for a focus point
to focus at a particular point.. I often switch to manual selection of
which point that should be focused on... Is there a draw back to doing
this? why have 9 points? I think most of the time it tends to focus on
odd places like the hair or ears of a person, when I really want to
focus on the eyes..

Any clearafication is appreciated

Soren


Yes.

5, 7, 9, 11 point focussing is all part of the sales spiel for the techno
buyers who must have the highest spec. Of even less importance than the ever
increasing number of pixels.

If you know what you are doing, 1 focus point is all you need. I would
advocate only ever using 1 at a time, but it is sometimes convenient to
select an off centre point, so there is some justification for having more
than 1.

Roy G

That's true for static subjects etc. but for sports/photojournalism
etc. modern cameras use the multiple off-centre focus points to
(atempt to) lock onto a moving subject and keep it in focus even if it
is not kept within the same position within the frame.
  #10  
Old April 28th 07, 08:17 PM posted to rec.photo.digital
Morton
external usenet poster
 
Posts: 70
Default Are many autofocus points nessesary??

Paul Repacholi wrote:
Soren writes:

certain composition. But for still photos I can use the center point
and move the camera (as I do now) without getting into trouble.


Canon have recomended against this, and have said that for best AF
accuracy you should NOT focus and re-frame, but to use the AF point
in the best position.

They are wrong. Using many focus points can lead to the classic sharp
wall behind the 2 foreground people's blurred faces.

Morton
 




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