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Archive 2012 · D4/D800: 3D vs. 51-point dynamic mode?
  
 
fhammond
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p.1 #1 · D4/D800: 3D vs. 51-point dynamic mode?


Hi all,

I asked a question earlier about autofocus on the D4/D800 (here). I've got a more general question about autofocus though that I'm hoping for some help on:

What's the difference between 51-point dynamic-area AF and 3D tracking?

In the manual is this:

51-point: "Choose when photographing subjects that are moving quickly and can not be easily framed in the viewfinder (e.g., birds)."

3D tracking: "...the camera will track subjects that leave the selected focus point and select new focus points as required. Use to quickly compose pictures with subjects that are moving erratically from side to side (e.g., tennis players)"

That sounds pretty similar to me. In 51-point mode, if I focus on an object, then pan the camera, I see the object stay in focus (despite the original focus point still being highlighted). If I review the photo on the camera (with the option to see focus points on), I can see that a different focus point actually as been selected.

So what is the benefit of 3D tracking when would you use it instead of dynamic AF?

thanks,
Fergus



Aug 16, 2012 at 01:51 AM
Guari
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p.1 #2 · D4/D800: 3D vs. 51-point dynamic mode?


I can say that I have tried both and 3D is like magic. If it moves, I use 3D over any other mode.



Aug 16, 2012 at 07:51 AM
canondoc
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p.1 #3 · D4/D800: 3D vs. 51-point dynamic mode?


Just be careful to not use the 3D mode while wearing 3D glasses, or the universe might collapse.


Aug 17, 2012 at 03:14 AM
form
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p.1 #4 · D4/D800: 3D vs. 51-point dynamic mode?


Do you select your own single starting focus point in 51-point mode? You can do that in 3d mode.


Aug 17, 2012 at 03:44 AM
Rags Hef
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p.1 #5 · D4/D800: 3D vs. 51-point dynamic mode?


canondoc wrote:
Just be careful to not use the 3D mode while wearing 3D glasses, or the universe might collapse.


No way... But there is a rumor that they have run into their own butt....



Aug 17, 2012 at 04:49 AM
RKnecht
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p.1 #6 · D4/D800: 3D vs. 51-point dynamic mode?


I've tried both modes on the D3 and D4 and neither has produced satisfactory results for what I shoot. I always use dynamic 21 or 9pt AF with varying focus lock settings.


Aug 17, 2012 at 11:25 AM
trenchmonkey
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p.1 #7 · D4/D800: 3D vs. 51-point dynamic mode?


RKnecht wrote:
I've tried both modes on the D3 and D4 and neither has produced satisfactory results for what I shoot. I always use dynamic 21 or 9pt AF with varying focus lock settings.

Agree 100% Does anyone REALLY want the camera selecting the exact focus point for them
Shooting w/ 9 pt, if I wanted more keepers...I'd use a 2nd body Maybe shootin' f11/f16 all the time
it might have its merits, but I live in f2 thru f5.6 land...and 3D/51 pt's a standing joke there.



Aug 17, 2012 at 11:45 AM
Steve Perry
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p.1 #8 · D4/D800: 3D vs. 51-point dynamic mode?


For my bird in flight shots, seems like dynamic 21 point works about the best for me. I have played with 51 pt and 3D settings but didn't see any improvement and in many cases it didn't seem to work as well. (Although I admit I haven't played with it much on the D4 yet - at least not to the extent as my D3 sereis cameras)


Aug 17, 2012 at 01:20 PM
dj dunzie
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p.1 #9 · D4/D800: 3D vs. 51-point dynamic mode?


trenchmonkey wrote:
Shooting w/ 9 pt, if I wanted more keepers...I'd use a 2nd body


+1, and . You are a wordsmith like no other TM!!!



Aug 17, 2012 at 01:28 PM
 

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trenchmonkey
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p.1 #10 · D4/D800: 3D vs. 51-point dynamic mode?


thanks a lot, DJ Please note: it WAS highlighted (in bold) for your perusal.
You should read my oldest Daughter's blog she makes ME look like I'm tongue-tied.



Aug 17, 2012 at 06:51 PM
Guari
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p.1 #11 · D4/D800: 3D vs. 51-point dynamic mode?


In 3d af-c you select the point, no auto selection made by the camera. At least on mine

It tracks wonderful, at least for ny uses.

I usually use the center point in afc 3D, focus let's say in the eye and with the af on, recompose. Then it will have kept the eye in focus (kind of dificult to put in words what would be so easy to explain while seeing a demo). Good stuff.



Aug 17, 2012 at 06:55 PM
gugs
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p.1 #12 · D4/D800: 3D vs. 51-point dynamic mode?


trenchmonkey wrote:
You should read my oldest Daughter's blog she makes ME look like I'm tongue-tied.

I can't believe this is even possible

Guy



Aug 17, 2012 at 08:20 PM
trenchmonkey
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p.1 #13 · D4/D800: 3D vs. 51-point dynamic mode?


thanks, Guy.


Aug 17, 2012 at 10:45 PM
fhammond
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p.1 #14 · D4/D800: 3D vs. 51-point dynamic mode?


So it sounds like none of us actually know the answer to this question! In both modes you select the initial activation point but it's not clear to me what happens next.

Anyway, it sounds like it probably doesn't matter as most people (including me) seem to get better results limiting the selection to few points.



Aug 18, 2012 at 05:17 AM
ausemmao
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p.1 #15 · D4/D800: 3D vs. 51-point dynamic mode?


Dunno whether the D4 has the same difference, but on the D7000, the difference is in what you're trying to do. 3D tracking will follow the initial target until you choose to refocus on a new target, even after changing position in the frame permanently.

39 (in your case 51) point will use other focus points if the target leaves the chosen sensor, but if you keep your subject off the selected AF point for an extended period it will change its target to whatever is under the AF point.



Aug 18, 2012 at 08:24 AM
fhammond
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p.1 #16 · D4/D800: 3D vs. 51-point dynamic mode?


Ah, that makes sense. I'll have to try it out. Thanks.


Aug 18, 2012 at 08:25 AM
Alan321
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p.1 #17 · D4/D800: 3D vs. 51-point dynamic mode?


3D AF mode uses the metering colour sensor to help track the subject by its colour and brightness. It can even work outside the area covered by the AF sensors but without the benefit of the AF sensors. The AF sensors manage the contrast info and the metering sensor manages the colour info. Together they can work very well if the subject is a different colour or brightness from the background or presumably if the subject is also a lot smaller than what an AF sensor covers. The on-board computer is managing both lots of data.

The colour and brightness of the subject is determined by knowing what was at the selected AF sensor when AF was first started, so it pays to be aiming at exactly the right part of the subject with the correct AF sensor when you do start the AF. You get to choose the starting AF sensor.

To speed things up the AF system uses a number of AF sensors that surround the chosen sensor but if the subject drifts too far away from the chosen sensor then it can lose the subject and chooses a new subject with your selected sensor. Too bad if it not then pointing at what you want to focus on but generally you will be trying to keep that sensor on target. With the 3D tracking mode it is less likely to lose the subject but conversely it is less likely to know that you actually want to focus on a different subject. In that case you should stop the AF, re-aim and restart it.

An advantage (or disadvantage, depending on your requirement) of the 3D tracking mode is that after you select any focus sensor, aim it at the intended subject and start the AF, you can recompose your image while keeping the AF active and the AF system will pick a new "selected" AF sensor that is still on your original target. This saves you having to select a different AF sensor for each composition. And the system still tracks subject/camera movements about that new selected AF sensor.

Depending on how you like to operate, 3D tracking can be very useful or a pain.

- Alan



Aug 19, 2012 at 01:32 PM





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