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01-18-2010, 03:48 PM   #1
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I don't get this multi point af stuff......

Why is 11af points better than 9 which is better than 5 etc?

I don't understand the concept of more than one focus point. Why would I ever want anything other than center point focus?

If your 11 af points fall on 11 objects at different focal distances how does the camera choose the focal point? Does it average? And wouldn't the depth of field have a bearing on how an 11 point af would look?

Confused in CA.....
ken

01-18-2010, 05:18 PM   #2
Ole
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I'm with you. I only use the center point so that I get to decide what will be in focus!
01-18-2010, 05:30 PM   #3
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It's a bullet point on a list of features. For those who use the camera in green mode (and there are a suprising number of them, they're just not on this forum), having all those focus points increases the chances of focusing on the right thing... maybe. In my experience, it just increases confusion.

In a studio scene where the camera is mounted on a tripod and is aimed very carefully, but where you want to change the focus to a sibject that isn't in the middle, then I guess the ability to use different AF points could come in handy. But in those situations, I either use Live View to move the focus point anywhere on the screen and focus that way, or I focus manually.

To each his own, though. If this forum has shown me anything, it's that there's no single "right" way of using your camera. I'm sure some people have neat ways of taking adcantage of multiple focus points.
01-18-2010, 05:31 PM   #4
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User selectable AF points ---

Well lets see, if I am using say f1.4 the dof is tiny. Lets say I want to frame my daughters face on the right side looking towards the left.

If I center point focus on her eye and the recompose the shot by turning the camera to the left, then her eye is no long exactly in focus. At F5 it might not be a big deal....

But if I select an af point on the right side of the viewfinder, I can frame the shot in the veiwfinder and actually focus on her eye without moving the camera and the Plane of focus.

That is when I use it. Also comes in handy on close up flower shots / bug shots where you dont want the flower in the center of the frame but want it perfectly in focus.


As I said at F5 not a big deal... but focus / recompose is less than great at shallow dof and the selectable af points are big IMHO.

Now AF letting the camera select what focus points it wants out of eleven... well that is not something I would do.

01-18-2010, 05:35 PM   #5
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ooh, good examples...
01-18-2010, 05:48 PM   #6
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If I'm understanding your question correctly, your camera doesn't use the 11 points at the same time. You have to choose one of the 11 points at a given time. This comes in handy especially if you are using a tripod where it is difficult to center focus, then realign.
For example, you're set up on a tripod and your subject is off to the right (rule of thirds). It is easier to use the point over the subject instead of the center point.
01-18-2010, 05:53 PM   #7
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Aha, maybe that's my first massive mis-understanding.

Only one of the eleven is used at any one time - makes sense.

Thanks for the examples folks....
01-18-2010, 05:59 PM   #8
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QuoteOriginally posted by Gillies Quote
If I'm understanding your question correctly, your camera doesn't use the 11 points at the same time. You have to choose one of the 11 points at a given time.
That's not quite true. Again, using the Green mode example, the camera will sometimes pick more than one focus point at the same time and average between them. You can see the multiple focus points flashing in the viewfinder when this happens. The same is true if you have the focus point selector set to "auto", which is a setting I particularly despise.

But *I* never use Green mode! I just tried it out to see what kind of results it gave.

01-18-2010, 07:23 PM   #9
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Hi Kace,

Each of the focus modes can have a legit use. I use Multipoint Auto for birds in flight, and suppose it might be useful for other rather quick moving subjects. The camera will generally choose the closest object in the viewfinder, so a bird flying a significant distance from background trees will be found by the AF system and used by the AF system. You must first obtain an initial focus though, and keep the subject in the VF frame throughout the series. An OOF first shot will result in a whole series of OOF shots. . . I don't know about anyone else, but I'm just not good enough to keep a flying bird dead center in the VF. . .

9 point and 5 point Auto can also be useful, if you can live with allowing the camera to choose the focus point -- each just narrows the range of focus points that the AF system can choose from.

Scott
01-18-2010, 07:52 PM   #10
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Like Igilligan, I mostly use the extra AF points for narrow DOF shots that I want to focus while framed, rather than focus, then frame (recompose). I recently let the camera use it's focus points to see what happens, and well... its the subject of this weeks PP challenge if that tells you anything.
01-19-2010, 03:04 AM   #11
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If you use a lens that doesn't have a flat focusing field, the extra focusing points are kind of important, especially when the subject is very close.
01-19-2010, 09:23 AM   #12
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Growing up with a manual camera with a split screen viewfinder, I naturally want to focus at the center out of habit and then move to recompose the scene if I want the main focus off center. I don't use the other focus points. I do like the feature of having the little red focus point flash however because on occasion I have inadvertantly moved the setting to SEL and it has prevented me from having a whole mess of out of focus shots. I can understand the value of selectable focus points and the examples mentioned but old habits are hard to break and I have never used the feature.
01-19-2010, 09:40 AM   #13
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On more advanced focusing systems (brands start with C. and N. ) the greater coverage (esp. on the Nikon with 51 points from what I hear) allows for computerized tracking of a subject as it moves around the frame - far superior for tracking a moving subject such as a bird in flight, or a race car, etc...
01-19-2010, 09:46 AM   #14
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the other application of AF points (instead of Center focus and recompose) is not to change perspective - not so much horizontally, but makes difference vertically. An example would be to focus on the person's face (using CF) and then tilt the camera to cover the whole body from head to toe; wonder why people look so short in the picture.

QuoteOriginally posted by matiki Quote
Like Igilligan, I mostly use the extra AF points for narrow DOF shots that I want to focus while framed, rather than focus, then frame (recompose). I recently let the camera use it's focus points to see what happens, and well... its the subject of this weeks PP challenge if that tells you anything.
01-19-2010, 09:49 AM   #15
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i'm assuming that you can only use the AF points on an auto focus lens, correct? a lot of my shots with my manual primes (A and M series lens) are not in focus where I want them to be. the AF selector won;t help in in this example will it?
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