My D4 doesn't want to continually track a subject that is travelling towards the camera or whose distance to the camera is changing quickly. When focussing on a subject moving towards me the camera will acquire focus straight away but will wait a couple of tenths of a second before re-acquiring focus and will repeat this wait-focus-wait-focus as long as I ask it to track the subject. I've found a number of tests on various blogs highlighting how good this body should be at tracking subjects with keeper rates in the 90's. I am getting something more like 10% that are close enough to being in focus to be useable for downsized shots. Tack sharp? Maybe 5%
I first noticed a poor keeper rate photographing motorcycles at a race track with TC's on my 120-300/2.8 OS. I put it down to the extender slowing what was probably an already average tracking lens and went back to panning where it performed very well (as long as I held up my end of the bargain).
Wathcing through the viewfinder I can see the focus change in steps and with the 24-85 I can feel the focus ring move each time the camera reacquires. The issue is more pronounced with objects well away from MFD. As you get within a couple of metres of the subject the camera adjusts much more frequently which leaves me wondering if it is something to do with the camera detecting that the target is no longer in focus before it tries to re-focus.
It's not an issue with front or back focus I believe - the camera with all of my autofocus F mount lenses will focus well on stationary subjects. Quick and accurate whether I'm using AF-C or AF-S, screw drive focus or HSM/AFs.
I've tried with motorcycles, cars at a race track, cars on a suburban street doing little more than 60kph, people running, people walking and even walking towards a subject such as a brick wall all with the same behaviour.
I try my absolute best to keep the focus point(s) on target and am confident that is not the issue.
When I initiate tracking has an effect on keeper rate but not in the manner I expect it should.
1. If I initiate tracking (e.g. AF-ON or shutter half press) for a second or two for the camera to build some trend of the subject's rate of closure it is a lottery as to whether the first shot is in focus or not. Subsequent shots are a lottery as well
2. If I shoot straight away, there's a good chance the lens will lock quick enough for the first shot and then subsequent shots are a lottery.
In fact this has gotten me to the point (as a previous BBF only shooter) that I have a second Settings Bank setup with AF working off the shutter button
Release or Focus priority (Custom Setting A1) doesn't make any difference. In fact the camera will quite often still fire in Focus priority even with an out of focus image. I've found a number of threads and blogs on that particular quirk of the D4 but none of the suggested fixes have made any difference to the operation of my camera.
Settings:
AF-C
I've used just about all of the point combinations I can think of: 3D, 51, 21, 9 and single, on centre, off-centre in the cross sensitive zone and off centre on the sides
I've tried removing AF actuation from the shutter and working with AF on the shutter button
I've tried each of the 4 settings in the A1 custom menu (release/focus priority) and also the A2 menu (just in case that made any difference)
I've tried each of the time settings in the A3 custom menu including OFF
High speed frame rate set to 10fps and low speed anywhere from 9fps down
Manual or Aperture priority with AutoISO and shutter speed high enough to stop motion
Firmware: A 1.10; B 1.10; L 1.009
Lenses:
Sigma 120-300 OS - this was the first lens that I noticed the issue on. Was used bare, with a Sigma 1.4x and with a Sigma 2.0x tc at different times.
Nikon 24-85 f/2.8-4.0 AFD
Nikon 80-200 f/2.8 AFD (the first push-pull design)
Nikon AFs 35 f/1.8G DX (I know it's a crop lens but it's my only AFs lens)
The only difference is with the 2.0x tc slowing things down and making it a bit worse
Next steps
I'm going to write down all of my settings tonight and give the camera a full reset and re-load the latest firmware. On the way into work in the morning I'll test again with oncoming traffic.
My next step if the full reset and firmware don't make any difference will be to hire a 70-200/2.8 VR2 for the weekend. I've only got the 35G DX as an AFs lens so want to confirm with some pro glass.
I will also test with vehicles and people travelling away from me. I can't remember seeing the issue on a recent track day shoot but wasn't shooting much of the back of cars so didn't really take much notice.
I don't hold much hope for any of these steps solving the problem for me but want to go through them before talking to Nikon about dropping it in for service. I'm not a pro so don't have NPS membership (just an amatuer with bad GAS) and the camera was bought used and is old enough to be out of warranty so the prospect of testing out Nikon Australia's customer service and price is a bit daunting. That is the main reason this wasn't addressed back when I first noticed it.
I've tried a number of different internet searches and haven't found anything to suggest others have had this issue with the settings I've tried. I ran across one blog which described "doesn't focus as well as my old D3" and ended up with the author settling on 9 points, Release priority (counter intuitive I know), focus lock timing set to very short or OFF and frame rate at 9fps. Those settings don't make any difference for me unfortunately.
Does anyone have any thoughts on the matter?
I'll be keeping this thread up to date with my progress for the sake of anyone in future who may run across this issue.
Thanks for reading
