Focus Point Confusion

gingergirl

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Hello.... I've always used a single focus point. I am a new E-M1 user and I don't understand when it would be advantageous to use 9 focus points or even all of them, how they work together, and how the camera would know what you want to focus on if you are using multiple focus points. I'm just not getting it.
 

2112

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When I shot with my 7D I would use the zone focus point's for inflight birds and aircraft. It gave me a better chance at catching a good shot over trying to keep up with whatever I was shooting using only one focus point. I have not tried this using my E-M10 and not sure this focus system would be fast enough for that, but I will have to give it a go sometime and see..
 

lightmonkey

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Hello.... I've always used a single focus point. I am a new E-M1 user and I don't understand when it would be advantageous to use 9 focus points or even all of them, how they work together, and how the camera would know what you want to focus on if you are using multiple focus points. I'm just not getting it.
we dont know -- which i why i dont use multi-point focus in the first place -- but we can speculate: i imagine on it can sample a few points (via contrast detect), and focus on the closest point. and/or it can build a rough profile of the 2d field and focus on the closest prominent object. this is an easy algorithm to implement.

if you stick with a single point [rectangle], but change the size of the rectangle [=larger], it helps focus faster because theres likely more areas of high contrast to catch onto. in most situation there isnt enough DOF difference to justify miniature focus point vs larger one.

small group focus (like 3x3 = 9 point) works well for most people since it covers their subject which is usually a human centered in the frame.

the full multi-point focus i imagine could be useful if youre shooting people, but you need to focus fast , dont have time to focus-recompose, and dont shoot with the people centered.... like a street scene.

however, nice thing about EM1 is that it has face/eye-detect that works quite well. [the tracking on the other hand...not so much]

what this means is i use center-point focus, with face-detect on. if im shooting static scene, i have time to focus-recompose. if theres people in the scene, the face-detect will catch it for me. best of both worlds
 

owczi

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@gingergirl: you're not alone here. The default behaviour is a' la compact cameras. I also use single point by default, and a lot of people (most?) do.

The great thing though is that you can define an AF home position of your choice and map a key to it. What's even better is that when you move the AF point, you can then toggle between that point and your home point with the key at your will. I find this extremely useful for events where you have a main target and a secondary target occasionally appearing.

The face detection is great but in some cases it can be your enemy, when you have a scene with mixed content i.e. faces and stuff that's not faces. All comes down to knowing what you're doing.

As to the multi-point, I think there must be some good use for it, but I for one just haven' found it yet :) But think of it as a single point, just a very big one. Same rules apply - same thing: with a single point focus, what part of the focus point is used? :) The 3x3 multipoint (or in other words, the 9x size focus point!) can be helpful in a tricky scene with a lot of uniform background for example when contrast AF can fail if it has nothing to catch on, and the next thing to catch on is outside the single point.
 

DennisC

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I'm new to Olympus bodies so my new E-M10 is still a learning curve.
What I learnt from the Asian website is that the 9 point focus has been optimised for tracking ( with the M10 ).
At least that's my take on it. Here's the quote:

You can switch from 81-point AF to 9-point group target AF. This mode is better for tracking the subject than the single target AF, and so, for example, you can track a running child. The AF tracking ability has been improved by enhancing the group target AF algorithm.


Source:
http://asia.olympus-imaging.com/products/dslr/em10/feature/05/
 

DL Photo

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I'm new to Olympus bodies so my new E-M10 is still a learning curve.
What I learnt from the Asian website is that the 9 point focus has been optimised for tracking ( with the M10 ).
At least that's my take on it. Here's the quote:

You can switch from 81-point AF to 9-point group target AF. This mode is better for tracking the subject than the single target AF, and so, for example, you can track a running child. The AF tracking ability has been improved by enhancing the group target AF algorithm.


Source:
http://asia.olympus-imaging.com/products/dslr/em10/feature/05/
You can't take those comments to heart though.If the background is very busy (lots of contrast) you are best using a single AF point so that the camera can focus on exactly what you would like it to focus on. If there are trees or stands behind the runner on the track, the camera may get confused and focus on what is behind.

If the background has less contrast......a good example is taking pictures of birds in flight......the background will be the sky (which has less contrast). In this case, it is nice to use the group focus points as the camera will try and focus on the object that has more contrast.....in this case the birds.

The same goes for static subjects. The camera will find it easier to focus where there is more contrast. For static subjects, I always use single point focus. You can always focus and then re-compose if you want your in focus subject to be left or right in the frame.

Your best bet is to test it out yourself. Go to a dog park and try to take pictures of the dogs running around. Use single point and then use 9 point........use the different settings and see which works best for your set up.
 

OzRay

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Each of the four available focal point options provide for varying subjects. The two single points for when precision is required, the nine points for subjects like groups or where it's difficult to hold a single focus point, and the full array for things such as aircraft in flight where the background is mainly sky or a mix of sky and cloud. A good way to understand how the focus points work is to shoot the same scene cycling through the different options and then watch what the camera decides to focus on. It can be quite surprising, especially with the multi-point options. You can take shots and later view the focus points by opening up the shots in Viewer or Master (I think even Lightroom shows the focus point selected).
 

yakky

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Single point is great for photographers. Hand the camera to a friend, it's time to place your bets on the camera!
 

gingergirl

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Wow! Great responses. So far only the single focus point has given me the results I've wanted (the 9 kept jumping everywhere but on my subject), but I've only had the camera for a few days and haven't had a chance to try out many different scenarios. As suggested, I will try a controlled approach to see if it becomes clearer. Thanks.
 

gingergirl

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@gingergirl:
The great thing though is that you can define an AF home position of your choice and map a key to it. What's even better is that when you move the AF point, you can then toggle between that point and your home point with the key at your will. I find this extremely useful for events where you have a main target and a secondary target occasionally appearing.
Well this is a great idea. Which button did you map to do this?
 

jnewell

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I'm curious too. I have F1 set up as my 'return to home position' button for the focus point on both my OM-D bodies, but I haven't figured that trick out.
 

yakky

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The great thing though is that you can define an AF home position of your choice and map a key to it. What's even better is that when you move the AF point, you can then toggle between that point and your home point with the key at your will. I find this extremely useful for events where you have a main target and a secondary target occasionally appearing.
Wow, great tip. I remember seeing that option and thinking why would I want to waste a button for that, but I never though about the toggle aspect!
 

DL Photo

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I've always kept my focus point at the center of the viewfinder / screen. I focus on the subject.....recompose....and then take the picture. Don't see a need to move the focus point around the screen....but what works for me may not work for others. This technique works really well with back button focus (I have back button focus set to one of the Myset's).

Just another suggestion.
 

jnewell

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I've always kept my focus point at the center of the viewfinder / screen. I focus on the subject.....recompose....and then take the picture. Don't see a need to move the focus point around the screen....but what works for me may not work for others. This technique works really well with back button focus (I have back button focus set to one of the Myset's).

Just another suggestion.

The situation in which I've moved the focus point is where I'm taking a series of photos and the in-focus subject is not in the center of the frame (which is often). Yes, I could focus/recompose, but if I'm taking a series of photos that's at best wasted effort and in most cases would result in lost shots.
 

gingergirl

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Ok, so I just learned that holding in the Ok button for about a half a second will return the focus point back to the center. Love!
 

tosvus

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Single point is great for photographers. Hand the camera to a friend, it's time to place your bets on the camera!
Absolutely. I make this mistake all the time, handing the camera to my wife, and when she takes a picture of me and my daughter she usually manages to put the focus spot between us...
 

owczi

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I've always kept my focus point at the center of the viewfinder / screen. I focus on the subject.....recompose....and then take the picture. Don't see a need to move the focus point around the screen....but what works for me may not work for others. This technique works really well with back button focus (I have back button focus set to one of the Myset's).

Just another suggestion.
We all shoot differently, that's a given. There are cases where the half a second needed for focus and recompose means a missed opportunity. There's also the focal plane which is a flat surface and at certain DoFs and certain situations where subject is far from the center of the frame, recompose may mean that the shot is out of focus. This is rarely an issue, but it does happen.
 

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