"D7000 Dynamic Area AF - friend AND foe" Tue 29-Mar-11 02:57 PM by rasworth
I have watched with interest the evolution of Nikon DSLR autofocus modes, from the D70 thru the D200 and D300, and now the D7000. In particular, I have observed the lack of information wrt dynamic area af. So I am creating this diatribe to attempt to clarify, or at least start some discussion.
I have experimented with, and read several references about, D7000 dynamic af, including the Nikon tutorials, Nikon manual, and Thom Hogan's ebook. Without exception all describe its usage wrt moving subjects, and none point out that the camera can't tell the difference between a fixed camera position with a moving subject, and a fixed subject with a moving camera. In the latter situation dynamic area af can be a plus or minus, depending upon the photographer's awareness or lack thereof.
As an af-on only (focus removed from the shutter release and transferred to the AE-L/AE-E button, always in continuous focus mode) focuser I avoid using dynamic area af for static subject shooting. The reason is I tend to keep my thumb pressed on the AE-L/AE-E button as I scan around the scene for the appropriate focus point, and if I am in 9/21/39 dynamic area af it is very easy to "hook" focus on the wrong object, particularly if it is closer than the final desired subject. Again, the camera can't tell the difference between a moving camera and a moving subject, and therefore will tend to lock on the object under the focus target at intial button press, even though one slides off to another target. IMO this is one of the reason for at least some of the complaints about D7000 mis-focusing.
On the other hand one can use dynamic area 3d to lock on one object, say the subjects eye, and recompose without losing the desired focus target. It's almost eerie to watch the focus rectangle jump back to the original focus point during recomposition of the scene. I haven't used this capability extensively, but in my limited experiments it seems to work well.
My main message is don't leave your camera in dynamic area af thinking that it won't affect static shooting and will be there for moving objects, particularly if you are an af-on only focuser. It can easily work against you, and therefore I recommend the default setting for one's D7000 to be single area af.
Added by edit - attached a slanted brick wall shot to illustrate the 3D 39 point capbility, started with the center rectangle on the tape and moved the camera, kept thumb pressed on AE-L/AF-L button and tape area remained in focus.
Added by second edit - I stand (or sit) corrected, upon re-reading Thom Hogan's ebook I found a reference to using 39 point 3D for reframing people shots.
#1. "RE: D7000 Dynamic Area AF - friend AND foe" In response to Reply # 0
>Without exception all describe its >usage wrt moving subjects, and none point out that the camera >can't tell the difference between a fixed camera position with >a moving subject, and a fixed subject with a moving camera.
In many situations, it is possible to distinguish between the two; in particular when your moving subject is in front of a static background.
If the camera is moving, everything in the frame changes position relative to it. If the camera is still, only the subject changes position and the background is static.
>As an af-on only (focus removed from the shutter release and >transferred to the AE-L/AE-E button, always in continuous >focus mode) focuser I avoid using dynamic area af for static >subject shooting.
Agreed! Single-point AF is better for static subjects - which is what Nikon recommend on page 94 of the D7000 manual.
>On the other hand one can use dynamic area 3d to lock on one >object, say the subjects eye, and recompose without losing the >desired focus target. It's almost eerie to watch the focus >rectangle jump back to the original focus point during >recomposition of the scene.
I've not tried that. I wonder if it works as well on other Nikons?
#3. "RE: D7000 Dynamic Area AF - friend AND foe" In response to Reply # 1
I agree the photographer can usually distinguish between moving subject and moving camera, but my point was the camera does not differentiate between the two, thus the "trap" when using dynamic area af and AF-ON only technique.
It baffles me why Nikon chose to show the moving focus rectangle in the viewfinder for 3D, but not for the "simpler" 9/21/39 modes. If they had done so then it would be obvious when the focus slipped to another object.
#4. "RE: D7000 Dynamic Area AF - friend AND foe" In response to Reply # 1 Tue 29-Mar-11 04:57 PM by rasworth
I don't remember for sure, but I believe the 51 point 3D mode on the D300 did not show the moving focus rectangle when in continuous servo mode. The continuous visibility is what makes the mode "work" IMO, one always knows the focus target location.
I convinced my not-so-willing subject to go outside for a trial usage of the 39 point 3D mode, works very well particularly in outdoor lighting. Started focus on her face and panned sideways, snapped the picture. The rectangle stayed on her face.
#5. "RE: D7000 Dynamic Area AF - friend AND foe" In response to Reply # 2
I have become tired of trying to outguess the camera or predict what it will do when it is in automatic modes. I now mostly shoot with the single centered point as my AF target and use the AF-On button to decide when I want the camera to be focusing and when not. I have developed the habit of setting focus and then recomposing. This doesn't work well in two situations:
1. When recomposing significantly changes distance from camera to subject. 2. Sports shooting, when auto tracking by the camera does a lot better than me
#6. "RE: D7000 Dynamic Area AF - friend AND foe" In response to Reply # 5 Wed 30-Mar-11 01:28 PM by rasworth
I'm in agreement with you, generally use the same technique. I do intend to explore the 39 point 3D mode further, expressly to counteract the problem you stated in (1.). At least for my sample portrait photograph it allowed me to both recompose and maintain ongoing focus on the subject. It appeared to be an automatic version of manually moving the focus rectangle to one side of the frame.
Added by edit - at the risk of being redundant, I will say this is the first automatic mode I've encountered that seems to work well in conjunction with the AF-ON only technique.