Multiple focus points

rogertb

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Roger
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Hi chaps, I so often read advice reference focusing points, this is a typical comment from a 7D user about the 19 point af "I see so many problems with this, greatest of all the complete loss of control" and more often than not the single centre point is recommended, I have my camera (550d) set on this ALL of the time and I'm wondering if I'm missing something ... anyone help me out here please ? Roger
 
If the lens has at all shallow depth of field it can't be simultaneously in focus on several points in a scene.
If you let the camera decide which spot to go for it might not be where you particularly wanted to be a sharp as possible.

I don't know the 7D but I guess like 5D the spot which is locked on will flicker.
If you use the centre spot to pick a focus point then re-compose, or alternatively select which spot is 'right' and switch the others off for the shot you have control again.
Or manual focus instead!
 
You can always manually select which of the 19 or however many AF points you have you want to use :)
Using the centre point and recomposing is not always optimal, especially at shallow DoF, when you can actually shift the focal plane signficantly or for tracking moving subjects (you may pick a AF sensor at the top of the frame for example to track a runners head).

You don't have to use full manual focus to take control back from the camera.
 
I have a 7D and mine is set to single AF point with surrounding assist points, I don't think this is available on the 550D however I don't think you are missing out, the important factor is you want to decide whta is the focus point not some random selection by a multiple point AF system. I think people get overawed by these choices, the camera is not clairvoyent it has no idea what is important to you, so I would say pick your own AF point, centre or otherwise and stick on your target.
 
on the 7d if I'm doing portraits or anything that isn't moving I will try to use single point centre and reframe but to be honest im getting lazy so i frame and move the AF point on camera. i did this recently with my F4 70-200 wide open and produced the sharpest eyes on portrait type shots i've ever managed without using Centre points once.
if something is moving around a lot, cars etc I would use multiple grouped points with the servo modes I'm not good enough with panning and single point.
 
Thanks chaps, I think you've confirmed my suspicions, Canon develops these extremely clever 'focus devices' but nobody seems to use them except, I guess, when the camera's locked off on a tripod where the ability to move the AF point is important. Thanks for helping me on this ... Roger
 
I don't think it is a matter of Canon developing extremely clever focus devices that nobody uses but more a horses for courses situation.

Depending on what situation I am in I will use just the centre AF point, in another situation I will utilise one of the other AF points. In other situations I will use all of them.

Steve
 
Thanks chaps, I think you've confirmed my suspicions, Canon develops these extremely clever 'focus devices' but nobody seems to use them except, I guess, when the camera's locked off on a tripod where the ability to move the AF point is important. Thanks for helping me on this ... Roger

Hi

It's not just Canon, the Nikon D700 has 51 AF points, 3D tracking etc etc.

As above really, it is very much dependant on what your shooting / what the circumstances are as to which AF point / how many you use etc etc.

I generally use the Centre focus point for Motorsport, others for different situations etc etc.

The New 5D MKIII has gone from 9 points (MK II) to 61 points with 41 being cros type and I can't remember what the 1D series are...
 
rogertb said:
Thanks chaps, I think you've confirmed my suspicions, Canon develops these extremely clever 'focus devices' but nobody seems to use them except, I guess, when the camera's locked off on a tripod where the ability to move the AF point is important. Thanks for helping me on this ... Roger

The thing about auto modes is that they're really clever compared to someone who doesn't know what they're doing. Many users will be happy with them because they allow them to take OK pictures with a big complicated camera.

Forums are full of people who are learning or have learned to take control of their cameras to take better than OK shots. You'll see from some of the debates here that there is more than one way to take any shot and the camera is a complex tool that allows us to make these choices.
 
Thinking more about it I guess multiple points could be good for BIF - I've always struggled to get the centre point on the bird ... ?

Roger
 
I use my 7D a lot for taking aircraft from our local air force base as they're flying past. I've used single point, centre and outer, and multi point more recently to see how it came out. I was very surprized and pleased with the result but I wasn't using a particularly small DOF so I got a nice focussed photo throughout.
 
Interesting, I'll give them all a test, good idea going to the local airport (I have one near by ) Roger
 
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