51pt AF mode

[reaction]

Can anyone explain how the 51pt AF works on a D300s? When the tab is set to 51pt, the AF point marker is gone, and there's no way to know what is focused.

http://kenrockwell.com/nikon/d300/images/af-system/200_9779-sensor-mode-switch.jpg

No, I can't tell in the viewfinder what's in focus when it's dark and the subjects are moving. But with the other AF modes I can't focus and recompose a moving object. I switch orientation so can't use a side point.

I've always used the bottom 2 modes in the past.

[arthurking83]

It's a dynamic auto focus mode.
(edit: auto focus as in, choosing the point of focus or the subject to focus on ... not just focus distance)

It determines where to focus for you.
How this determination is made is known only by Nikon's engineers.

I've found that it's too inconsistent if there are many subject to focus on, and never use it.

When it finds something to focus on, it will light up the relevant focus points via the viewfinder, and there can be more than one focus point lit up at any one time.

[rellik666]

I have found it ok for fast moving objects...gave it a go for the first time a few weeks ago, but your right, it is more of a gimmick I think!

[kiwi]

Supposed to be good for say birds in flight - picking up subjects moving inconsistently across the screen

I also have used it, didnt like it much, and havent again

I use 9pt dynamic most of the time

[N*A*M]

the focus points won't light up if you are in AF-C mode

it seems to do face detection, and is also good at picking up an off centre subject against a clearish background
i set my camera to this mode if i ever have to hand it to somebody else who is not an experienced DSLR user

it is no good for tracking from my experience

[RRRoger]

51 point might be good for movie mode on the D4 if you use a lens/setting with enough depth of field.

[davidd]

I have recently changed to using the AF-ON button to initiate focus. This may help you in your situation.

To do this:

1. set your AF-Area mode to Dynamic (middle one).
2. Set your AF activation (Menu a5) to AF-ON only.
3. Set your Focus Mode selector (on front of body) to AF-C.

Now, the focus is initiated with the AF-ON button (use your thumb).
Centre the object you want to focus on (or move the AF point on to the object), and press the AF-ON button.
Hold this button down and you can move the camera to recompose, the focus will stay on the object.
If the object moves, the camera will track the moving object.
Keep holding the AF-ON button down, and press the shutter button whenever you want.

If you are not tracking a moving object, but want to focus and recompose, just centre the object, press the AF-ON button, and release it. The camera will stay focused at that distance, you can now recompose and shoot.

It takes a bit of getting used to, but once you are using it, you won't want to go back to using the shutter button to focus.

[reaction]

I use AF-C so it won't light up.

as I said it's for moving subjects, so I would love if I could focus, keep AF-On, recompose and see viewfinder light up which point it thinks the subject is, and shoot.

I find it frustrating so many things are disabled by AF-C, eg AF assist by mounted speedlights