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 p.9 #9 · UPDATE - Nikon D5/D500 Dynamic AF Issue | |
Steve Perry wrote:
OK, I think I finally have an answer. Before I lay it out though, I wanted to thank everyone who helped by posting to this thread and PM’ing me. A extra-special thanks to Snapsy and Keith for their help on this. Literally couldn’t have done it without them 
So, here’s what I think is happening, not sure if it’s 100% correct or not, but it seems to fit the facts and behaviors as we know them. Also, I reserve the right to revise this as time goes on : )
First, we know for sure that the D5/D500’s Dynamic area is not the same as the previous generation of bodies, no question there. In the past, you would typically acquire the target with the primary AF point, and then if the target slipped off that point, another AF point would jump in and take over – and it would track like that indefinitely.
The new system on the other hand seems to let go of the target and go for whatever is under the primary AF point – almost like Dynamic wasn’t even there. This tends to appear broken since when viewing the images in View NX-i or on the back of the camera, the system never seems to move the AF point – it always shows the selected point. (In the past, you could see the point it used.)
According to the EXIF data though, it actually is selecting different AF points as the subject leaves the primary point. However, it’s reporting it like Group AF does – just showing you where the selected area (point) is and not the actual AF point that was used. As Snapsy said, you can verify this with the EXIF Tool. The camera is unquestionably selecting different AF points as needed.
So, after looking at far too many lines of EXIF code and finally seeing a pattern, here’s how the new system works (I think  )
It locks on with the primary AF point and begins tracking. If the subject falls away from the primary AF point, the system will switch to one of the auxiliary points in the selected Dynamic area. However, unlike the old system, the new system has a bias for the primary AF point. After a brief delay, the camera tries the Primary AF point again. If there is a good target under the primary AF point, it will go for that. If there is not a good target under the primary point, it will go back to using the auxiliary points. It will continue to go back and forth like that until it can get a lock with the primary AF point again – or you stop focusing.
Two notes -
Note that it MUST be a good AF target for the system to switch – just a target that it can technically focus on isn’t good enough. I have tested this with poor targets the camera could just barely focus on. While the camera could technically get a lock, it would stutter a little trying to keep it. I would then switch to Dynamic and focus on a printed box with the poor AF target in the background. When I move my primary AF point over the poor AF target, it would stay with the first one indefinitely. Field tests also seem to confirm that it needs a good target in order to switch points – sadly, there are a LOT of those out there.
Delay time – In the past, the camera would not invoke the delay time (Blocked AF Response) specified under A3 unless the target had completely left the AF area. However, that’s not the case now.
The camera will start the countdown as soon as the target leaves the primary AF point (as a poster noted above) and use the auxiliary points until the time runs out – at which point it will try again with the primary AF point.
Usage
So, if this is the new normal, we have to adjust to the change. For some people, this system is actually an advantage, for others, not so much.
The advantage favors more experienced shooters. In the past with Dynamic, if the system switched to a different AF point, it would tend to stick with it – but sometimes that’s a problem.
With the old system, if I’m photographing a bird coming at me at a 45-degree angle, I would go for his head. However, if I accidently slide the primary point off, the system would pick a new AF point. If it decides to go to the spot on the bird down by where the wing meets the body, it was an issue. The camera would lock on and just stick there until you refocused – even if for the rest of the sequence you kept the primary AF point on his eye.
With the new system, it may still move to the wing, but if you keep the AF point on the eye, the camera will get the idea and switch back to it.
The downside of course is that if you really are having a difficult time tracking, in the past Dynamic would really help. Just get the initial lock and fire away. Even if the primary AF point never revisited the subject, it would continue to track and not jump to the background. IMO this is the better method – less experienced shooters can use wider areas and more experienced shooters would use smaller areas to restrict where the camera could focus.
So, the bottom line is this – with the new system, you need to do your best to keep the primary AF point on your subject. If you’re having a hard time, set the delay under A3 to 4 or 5. However, keep in mind even at “5” the delay is short. However, just knowing that it’s critical to keep the AF point on target may be enough to help some shooters.
Finally, keep in mind that this doesn’t mean I personally endorse the new system or even that that the thing isn't broken (I may just be documenting a bug). I'd actually like to see Nikon give us a choice between the two - maybe call the current one “precision dynamic” or something.
And as Forrest Gump would say, “And that’s all I have to say about that.”
...Show more →
Steve, thank you for your diligent work on reverse engineering the D5/D500 Dynamic Area modes! It was truly a pleasure working with you on this issue. Between Steve and me, we looked at over six thousand of my images taken of short-eared owls (and northern harrier hawks) in flight. These images were taken on three separate days, using either (1) the Nikon D500 and the Nikon 500mm f/4 lens (with 1.4x TC), or (2) the Nikon D5 and the Nikon 800mm f/5.6 lens. All these images were taken using the D72 dynamic area, with an A3 delay setting of either 4 (for the D500 combo) or 3 (for the D5 combo). Some of these images were shown here on FM:
https://www.fredmiranda.com/forum/topic/1476039
https://www.fredmiranda.com/forum/topic/1466192
Steve was carefully considering these real world usage images, in addition to performing more controlled experiments. I think Steve has described the D5/D500 Dynamic Area modes as correctly as possible. We may learn more moving forward, of course. I also think that Steve has correctly described the advantages and disadvantages of the new Dynamic Area AF system.
I think I only have two things to add to Steve’s summary. In my usage scenarios with owls in flight, the delay before the cameras attempted to switch back to the primary AF point was around a half second (A3 delay = 3) or very slightly longer (A3 delay = 4). My second point is that I plan to continue using the D5/D500 Dynamic Area modes for birds in flight. As my BIF tracking improved over the last year (my first year focused on BIF photography), I found the D5/D500 Dynamic Area modes working better and better for me. Now I know why - because I got better at keeping my subject over the initial AF point (not always easy with very long lenses).
Keith Williamson
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