Which focus point?

norahbattie

norahbattie

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Nads
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Hi,
I was wondering which focus point does everyone use? And do you have your focus button seperated from your shutter button. I went to a course recently and they said its better to have your AF-on as your focus button and have the centre focus point active rather than them all and recompose the shot. What does everyone else do?

When you are shooting parties is better to have them all active because you don't have time to recompose otherwise you miss the moment trying to get the composition right?

I have my 8 year old nephews birthday party coming up this weekend and might miss those 8 year olds running havoc around me! :gag:
Thx
Nad
 
As a Nikon user I use a rear focus button in af-c mode so as you release you lock the focus, the focus point depends on what I'm shooting as the D300 has lots :D
 
Its always best to have just one focus point, as only you know what you want in focus, choose the point that's going to be nearest the subject, focus-recompose if you need to.
 
I am a Canon user :D Got my first canon about 10 years and it gathered dust for 9 until I got the bug a year ago
 
I use focus-recompose, usually with the centre AF point, and via the back button.
 
:plusone:

Centre point AF and recompose the shot (when it is suitable to do this, which is more often than not)
 
For studio work I tend to use centre, everything else I use all of them, (but not at the same time)
 
Center focus point as its more accurate than all the others on a Canon body with a f2.8 or faster lens.
 
I generally use the center point, but will change as necessary depending on what I am shooting. I recently got the 7D and although I am far off understanding it as well as my old 400D, I'm fairly sure there is an option to have the camera autoselect the focus point, but from a selection of points (ie the middle 9) rather than all of them. This may be useful if taking shots at something like a party, where people will be moving all over the place. I guess this will be on the 5dII as well?

One problem with focus and recomposing is that at low apertures you can through out the focus. Another option with the 5dII is to shoot and crop to recompose in post processing.

As for separating focus from the shutter button, I've never tried, but it's on the list of things to have a go at.
 
Mike_J_Smith said:
I generally use the center point, but will change as necessary depending on what I am shooting. I recently got the 7D and although I am far off understanding it as well as my old 400D, I'm fairly sure there is an option to have the camera autoselect the focus point, but from a selection of points (ie the middle 9) rather than all of them. This may be useful if taking shots at something like a party, where people will be moving all over the place. I guess this will be on the 5dII as well?

One problem with focus and recomposing is that at low apertures you can through out the focus. Another option with the 5dII is to shoot and crop to recompose in post processing.

As for separating focus from the shutter button, I've never tried, but it's on the list of things to have a go at.
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Using auto-select for the focus point can be really useful if you're tracking a subject that is moving around the frame, on servo mode maybe. Just be aware that it will always pick the closest subject so for example if you're shooting football and another player moves in front, it will immediately switch to that person.
 
Dogfish_magnet said:
Center focus point as its more accurate than all the others on a Canon body with a f2.8 or faster lens.
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Depends on the camera, it is the cross type sensors which are most accurate, and most of the newer higher end cameras have more than one. The Nikon D300S/700/3S/X has 15 cross type out of the 51 focus points. The Canon 7D has 19 cross type sensors and the 1DS Mark IV has 45 cross type sensors. :eek: :lol:

Most of the mid range cameras may only have a single central cross type focus point, if they have one of that type at all. :shrug:
 
HoppyUK said:
Using auto-select for the focus point can be really useful if you're tracking a subject that is moving around the frame, on servo mode maybe. Just be aware that it will always pick the closest subject so for example if you're shooting football and another player moves in front, it will immediately switch to that person.
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That's not necessarily true, and depends very much on how you set up your AF. By reducing the AF Tracking sensitivity you can increase the delay prior to the camera switching to a new target. Here's what Canon says on the subject, with respect to the 7D. 1 series cameras will be similar....

C.Fn III -1 – AI Servo tracking sensitivity

This Custom Function has five levels, from slow to fast. The levels are:

0 = Standard sensitivity. AF will momentarily pause if the AF point sees another subject while tracking.
-2 = Slow. Tracking will pause for a longer period when AF is disrupted to allow you to find the original subject with the AF point.
-1 = Moderately slow. Pause length will be between -2 and 0.
+1 = Moderately fast. The AF system will respond faster to a change in subject position.
+2 = Fast. AF system will not pause. If the subject escapes the AF point, the camera will instantly re-focus on the area the AF point is currently covering.
The focus tracking sensitivity refers to how the camera responds and switches to another subject during focus tracking. This response sensitivity refers to how long the camera waits before switching to a new target subject when the current target subject escapes an AF point. It doesn’t adjust how quickly the autofocus tracks. The shorter the response time, the faster it will switch subjects to track a new subject. Therefore, if you want to quickly track changing subjects, set the sensitivity to a faster level.

However, if you want to track the same subject as much as possible without switching to another subject, set this sensitivity to a slower level to force the camera to continue tracking the same subject, even if a distracting subject enters the frame or if the subject is erratic and likely to escape from an AF point.

You should try each of the settings out to find the one that works best for you, but generally, you will find that setting -1 or -2 for fast moving, erratic subjects produces better results.
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Furthermore, you can adjust the AF Tracking Method to continue tracking your original subject, or to switch to a new subect if it enters the frame in front of your current subject.

C.Fn III -3 – AI Servo AF tracking method
With more than one AF point active, using either automatic point selection or manual point selection with AF point expansion, this Custom Function instructs the camera how to handle a second subject that may enter the focusing point area.

In some situations you may want the camera to obtain focus on whatever the closest subject is you are tracking (C.Fn III -3 -0). At other times, you may want the tracking to stay with the initial subject you focused on regardless of what else enters the focusing area, even if it is closer than the initial subject (C.Fn III -3 -1).

The options are:

0: Main focus point priority – with this setting, the camera will focus on any subject that appears under the main focus point, even if it is closer than the subject you were tracking.
1: Continuous AF track priority – as long as one of the expanded AF points can still detect the subject, the camera will continue to focus on it, even if there is a different subject covering the main, selected focus point.
Continuous AF track priority is effective for sports such as football or slalom skiing or anything where subjects are likely to enter the AF area in front of the subject being tracked.

Football players often cross in front of each other, which can distract the AF system. If you are tracking a player with automatic AF point selection and another player cuts in front of your main subject to tackle him, the player in front could distract the autofocus. With automatic AF point selection, the camera will select a different autofocus point in order to maintain focus on the first target subject. If the player appearing in front of the first target is at almost the same distance as the first subject, the camera may not be able to distinguish the distance difference and might lose the target subject.

The main focus point is defined as the first AF point to start focusing when using 19-point AF auto selection and AF point expansion. With Zone AF it is the active AF point.
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Apart from all that, using the AF-On button for focusing, rather than the shutter button, can also dig you out of that hole even if you don't have a more advanced AF system. You need quick reactions but it can be done.


As for which focus point to use, I usually use the one that can see sufficient contrast for reliable focusing and requires the minimum of recomposition. Example....

20100707_114803_.JPG
 
I have a 5D Mark II so basically you are saying use autofocus during movement (ie parties etc) and use single focus (when you have some time)?
 
tdodd said:
That's not necessarily true, and depends very much on how you set up your AF...

<snip>
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Sure, with some cameras there are ways of preventing the AF from doing what it is naturally programmed to do, so it is less easily foxed.

norahbattie said:
I have a 5D Mark II so basically you are saying use autofocus during movement (ie parties etc) and use single focus (when you have some time)?
Click to expand...

You mean auto select focus point, and single focus point?

I would only use auto select when you want to focus on the nearest part of the scene whether it's moving or not (bearing in mind Tim's caveat above) as that's what the camera will naturally try to do. For parties etc, I would say generally no.

In that situation, I would use single focus point and preferably the centre one provided it didn't then require too much recomposition. If it does, select another single focus point.

I have now been converted to using back-button AF, as Tim suggests. You re-assign AF only to the back button, removing that function from the shutter release, in custom functions*. Basically it separates the focusing and framing/shooting operations and prevents the camera refocusing all the time if you're not careful, sometimes on something you don't want it to if the situation is fluid.

* Give it a try. Here's a good link to setting up the AF back button function, which is a bit confusing without a guide! http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286
 
norahbattie said:
I have a 5D Mark II so basically you are saying use autofocus during movement (ie parties etc) and use single focus (when you have some time)?
Click to expand...

It is worth noting that the outer focus points on the 5D2 are not always very great, having only linear sensors rather than cross type sensors, making them completely blind to contrast in one plane or the other, depending upon which sensor it is. If the outer points can see contrast then they should work well enough, but if they can't then they are 100% worthless and simply cannot function.

e.g. if someone is wearing a hooped shirt then some outer AF points will have no problem focusing on the contrasty edge between the hoops, but other AF points will work perfectly. Turn the camera through 90 degrees and the sensors which did work will now not, and vice versa. If someone is wearing a striped top then it all swaps round again.

Therefore, when shooting in tricky or time sensitive situations with the 5D2 you may find more success by using the centre AF point only.
 
Thanks for the advice everyone, I have actually separated my focus button from the shutter button and found it is much easier but when I hand the camera to someone to take a photo I always forget to tell them and end up with a blurry photo..doh!!!

I have a few parties coming up so want to make sure I am doing the right thing by keeping it on centre focus. :)
 
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