AF-C

[desertstrike]

hi guys, i am having some problem with this AF-C mode

my equpiment is D90 + 70-300 VRII
i was trying to take some eagles flying past...

i would like to freeze the eagle... not panning...
i look through the viewfinder... half press the shutter release button
the camera try to focus... the eagle is continous flying..
i try to keep the eagle in the focus box by following the action...
once the eagle went out of the focus box, the eagle is not in focus...
then i try to put the eagle in the box again,
then i realised that the camera is slow in focusing on the eagle...
is it suppose to be like this?
or did i do something wrong?
as in method or something?

[zac08]

Is it too far and too small for the focus area?

If so, yes... you'll have problems focusing and locking on properly.

try this out with a larger subject on a straight trajectory like a car on a road. Once you have better practise getting a lock and tracking the subject, you may find it easier on the wildlife subjects which may jink or dive and make you lose track more often...

[desertstrike]

it is like imagine a semicircle, i am at the center of the circle, and the eagle is flying at the circumference... so the distance from me and the eagle is always changing, thats why the camera is constantly focusing to get a correct focus? and yes, it is rather small, if i zoom too much, and once it flew out of my viewfinder sight, i will have problem trying to locate it again...

[zac08]

Originally Posted by desertstrike it is like imagine a semicircle, i am at the center of the circle, and the eagle is flying at the circumference... so the distance from me and the eagle is always changing, thats why the camera is constantly focusing to get a correct focus? and yes, it is rather small, if i zoom too much, and once it flew out of my viewfinder sight, i will have problem trying to locate it again...

As mentioned... you'd need to lock on first before you can track continously...

Practise more first... Look for the subject, zoom in fully and lock on and keep tracking. Keep practising this and you'll get better.

[desertstrike]

Originally Posted by zac08 As mentioned... you'd need to lock on first before you can track continously... Practise more first... Look for the subject, zoom in fully and lock on and keep tracking. Keep practising this and you'll get better.

hmm... can u elaobrate what is meant by lock first?
is it keep the subject in the focus box, half click and hold until it focus?

[zac08]

Originally Posted by desertstrike hmm... can u elaobrate what is meant by lock first? is it keep the subject in the focus box, half click and hold until it focus?

Yes... you'd need to hold it in the active focus box first. Then half-press the shutter button and get the focus first. Once locked, then continue tracking as the subject moves.

[desertstrike]

Originally Posted by zac08 Yes... you'd need to hold it in the active focus box first. Then half-press the shutter button and get the focus first. Once locked, then continue tracking as the subject moves.

if it move out of ur active focus box, then have to repeat the process again ar?

[Simon_84]

the whole idea of tracking is to keep the target in your focus point all the time.

[desertstrike]

Originally Posted by Simon_84 the whole idea of tracking is to keep the target in your focus point all the time.

but but but... the box is so small... and the bird is so small as well...
is it better to use livew view instead? or worse?

[zac08]

Originally Posted by desertstrike but but but... the box is so small... and the bird is so small as well... is it better to use livew view instead? or worse?

Live view is worse...

If it's too small, then forget it... very difficult to hold it in the focus box, it must fill up the whole focus box at least.

The idea is to KEEP the subject in the focus box ALL the time.... this is called tracking.

[Simon_84]

Originally Posted by desertstrike but but but... the box is so small... and the bird is so small as well... is it better to use livew view instead? or worse?

if you wanna use live view then you badly need the tripod.
if the bird is too far away, don't bother straining your eyes, as you would probably need more than 300mm onwards.
else unless you want to crop then try using multiple shots and pick the best out of the lot.

[desertstrike]

simon_84 & zac08,

do ur feel that it takes quite long for the camera to refocus if the subject gets out of ur focus box?

[desertstrike]

and while half click to focus, can we zoom in and out? or must release shutter release button to zoom in and out?

[Simon_84]

Originally Posted by desertstrike and while half click to focus, can we zoom in and out? or must release shutter release button to zoom in and out?

when you half press your shutter button, is better not to zoom in and out.
want to zoom, do it first before pressing the shutter button.

[Simon_84]

Originally Posted by desertstrike simon_84 & zac08, do ur feel that it takes quite long for the camera to refocus if the subject gets out of ur focus box?

if your tracking is good, by right the lens motor or the AF-C wont move that much, provided the target is still roughly within the AF-point area.
once the motor stop adjusting, is probable a good time to take a shot.

[zac08]

Originally Posted by desertstrike simon_84 & zac08, do ur feel that it takes quite long for the camera to refocus if the subject gets out of ur focus box?

That's the hunting speed of both the lens and the camera. Better lens and cameras hunt faster. The others hunt slower.

[desertstrike]

Originally Posted by Simon_84 when you half press your shutter button, is better not to zoom in and out. want to zoom, do it first before pressing the shutter button.

i see... cos i heard abt this too... just wanna clarify...
but the irregular movement of the birds...
so often there is a need to readjust the focal length...

[desertstrike]

Originally Posted by Simon_84 if your tracking is good, by right the lens motor or the AF-C wont move that much, provided the target is still roughly within the AF-point area. once the motor stop adjusting, is probable a good time to take a shot.

i see. the motor will only adjust when the focal length is different ar?

[desertstrike]

Originally Posted by zac08 That's the hunting speed of both the lens and the camera. Better lens and cameras hunt faster. The others hunt slower.

ic... so my equipments are consider slow in hunting...?

[Simon_84]

Originally Posted by desertstrike i see. the motor will only adjust when the focal length is different ar?

er, i think you don't understand how your lens work...you set zoom to full tele at 300mm the lens SWM will adjust until it get a focus lock, once focus lock is achieved, the lens motor will stop moving.
so when you take a pic, less chances of having an non-sharp shot.