AF Points

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a lex

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Name
Alex
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Hi, looking for a few pointers as to selecting which AF points to use.

Normally I just leave it on the auto selection setting but looking back at a few of my photos its selected some strangely placed AF points meaning for example the eyes were out of focus. Now I was taking pictures of animals and as they were moving I was shooting at f4 so I know the DOF will be smaller meaning that less will be in focus but im wondering if a selected AF point would of helped?

Is it best to say use the centre AF point or is there a better way?

Also, a nice basic question (we are in the basic forum after all) but I often hear about focus and then recompose... could someone explain this simply for me as I feel it may of helped in this situation!

Thanks.
 
a lex said:
Hi, looking for a few pointers as to selecting which AF points to use.

Normally I just leave it on the auto selection setting but looking back at a few of my photos its selected some strangely placed AF points meaning for example the eyes were out of focus. Now I was taking pictures of animals and as they were moving I was shooting at f4 so I know the DOF will be smaller meaning that less will be in focus but im wondering if a selected AF point would of helped?

Is it best to say use the centre AF point or is there a better way?

Also, a nice basic question (we are in the basic forum after all) but I often hear about focus and then recompose... could someone explain this simply for me as I feel it may of helped in this situation!

Thanks.
Click to expand...

I use focus-recompose almost all the time. A lot of people do.

Select one-shot mode and a single focus point, then position it over the key subject area and half-press the shutter release. Focus is then locked on that distance so long as you hold your finger down. Recompose the picture as you want, knowing that the selected area is sharp.

You would generally use the centre focus point as that is more sensitive but you can use any. With a portrait for example, with the camera turned vertically, you want the eyes sharp and they are not going to be near the centre, so pick an outer point.

This works very well unless the subject is moving and changing distance, in which case you have to keep taking your finger off and on to track it, repeating the focus-recompose process (if depth of field won't cover the movement). Or switch to servo which will do that for you.

Automatic focus point selection can be useful, but also a bit hit and miss. It will usually select the closest subject area, or could get drawn to something bright and contrasty - neither of which may be appropriate.

Horses for course really - see your camera handbook. Most cameras offer basically similar operation but details vary.
 
To answer both points with one answer....

By selecting a single AF point you have control over where the focus is. You can place that focus point over the area you want in focus (the eye). This is where the recomposition comes in.....

by half depressing the shutter release button, this will lock the focus and you can then move the camera to get the composition you want, whilst maintaining the focus at the same distance.

If your subject is moving around a lot you need to recompose quickly to ensure the focus remains where you want it.

That probably makes no sense as I'm typing this at 0320 but I know what I mean.... ;)
 
Thanks for that video link it's cleared up a ton of questions I have had very simply. Especially on recompsure :)
 
That video is excellent, it really helped me with learning more about autofocussing. I try not to focus-recompose as drastically as I used to now..
 
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