D4 AF - Question to Pros

Started Apr 27, 2014 | Discussions thread
Grevture Veteran Member • Posts: 4,188
Sports shooter here, can feel you pain :)

jeminijoseph wrote:

I can't remember D300 had same issue.

Well, that just might be a bit of selective memory

These days I'm very curious about Canon side too. If 1DX is far better in wildlife auto focus, I don't mind switching. If D4s is the answer, I can upgrade too. Anyway I have to wait another year to upgrade or switch because of financial reasons.

The situation you show is always problematic, with any AF system. Keep in mind the AF system has no way of knowing what we want focus on. It assumes you want focus where the selected focus point(s) are at, and at the most significant contrast in the area it is covering. In your example, both the forest behind the bird and the bird itself is where the AF is pointing, and the at some point the forest offers the most obvious contrast. The AF does not see a bird, it just detects more or less strong contrast in the area at which it is pointed. As long as the bird had the sky as a back drop, there was no reason to refocus, when the forest, and that dark area appeared ... Bad luck.

As a sports shooter you quickly learn to hate ad signs, fences, nets and other busy backgrounds for pretty much the same reason, they are often just irresistible for a AF system

One thing you can do to at least partly reduce the incidence of series like the one you showed is to increase the delay before doing (drastic) refocusing (a4).

As things happen, the D4s will very probably be able to do this exact thing somewhat better: The new group AF mode is heavily geared towards always focusing on the closest of two possible distances in situation like that, meaning it will always choose the bird as long as you do not completely miss it with the focus points (in which case it is hard to blame the AF).

The 1Dx is ever so slightly better then the D4, simply because it has a focus mode very similar to the new group AF mode in the D4s.

BTW, one solution I'm using these days is to manually focus the camera while the subject is moving (help the camera a bit). Once the camera get the subject in focus, it may follow it. So I made some improvement there. Above pictures were from a trip to a Osprey nesting area couple of weeks ago. I got some nice shots in the trip (nothing worth going to the web site. So I put them in a temp folder

When I (occasionally) teach photography classes, and always insist that the 'A' in AF does not really mean 'automatic' but rather 'assisted'. The AF can help us focus, but it does not really ever know where we want focus, it can only make educated guesses. When I shoot sports, I often end up using AF in a 'semi-automatic' kind of way: For example focus on the feet of a goaltender in football (soccer), and then not activate AF when following the goalie making a save - since the net in the background is just to prone to trip up the AF.

The method you tried works, and help guide the AF making better guesses about what it is supposed to do.

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