[clarice629]

i bought the 24-70 last week because i felt ready for this lens.

im using the 40D thus my camera has only 9 focal points.

i noticed that when i focused on a spot and then move my camera to recompose the photo, my original focus would be slightly blur. i did it with both f/2.8 and f/8.0. when i use f/8.0 the situation does not seem as serious as when i use f/2.8.

what can i do? i only have 9 focal points and many times i do move my camera to recompose my shot.

is it my lens or is it my technique (i have shaky hands)?

thank you.

[jaegerlecoultre]

i dont understand why this is happening. i also dont know why it has anything to do with 9 focus points.

do u have the same problem with ur other lenses?

basically i assume ur using the centre focus point and hold down the shutter half way while focusing, without letting go the shutter button, hold and re-compose, and press it all the way down.

[叮噹仔]

我覺得你似用左AI servo 多d~~

[rankinelo]

clarice629 CHing,

This is absolutely normal. The depth of field is too narrow for f/2.8 and therefore the focus field should be moved slightly after recomposition.

There is no way to fix this problem except adjust the focus ring slightly to move it back to focus. However this requires practise :D

[HelloSRV]

Unless you are shooting close up thing, otherwise it won't be out focus because of the narrow depth of view after recomposition. Anyway, you can check focus accuracy by using focus ruler.

[clarice629]

C-hings, thank you for your comments. i think it's because i was shooting close-up at f/2.8.
i tried taking photos with f/8.0 with the normal distance and everything was fine.
i perhaps had overreacted but good to know that shooting close-ups at a large aperture has this phenomenon. thank you.

[HelloSRV]

I just want to poitnt out that 2.8F is usable in close-up and normal distance. However, recomposition while close up shooting may cause out focus.