James, we have the same lens as you, but use it on a D2Hs (I am
also familiar with MX, though not the D200 - our collection is an
F5, a D100 and the D2Hs).
Awesome lens, eh..? I love it..!
I am 99% certain your main problem is closest subject priority.
This setting is, in my experience, a can of worms, only to be used
when it really, really is needed (which is very unusual). Turn it
off and use either group matrix or spot, and I am sure the problem
will go away.
May be a difference in the cams, but. in retrospect, I had the same problem b4 using Closest Subject.
btw, I've found with the big Sig that shifting to centre-weighted
metering also helps. I've had some lively debates hereabouts about
whether metering affects AF, but, in my experience (and some
objective testing) it does. And you want to be metering on the
bikes anyway.
I had never heard of this. I use matrix/mult-pattern, and always dial in either -0.3 or -0.7 EV, to account for hotspots on shiney objects, like the tops of helmets, rims, etc.
I don't know if it affects focus, but matrix with a slight negative EV is accurate, with no blown highlights and good shadow detail 99.9% of the time for me.
In fact, after I take an initial meter reading on the available light, check the histo, then dial in the appropriate EV, and never have to check the histo again, even though I usually shoot about 300 images in a day, over about a 2 hour period. My point, I'd hate to lose this kind of metering efficiency. But I'll experiment with it, to see if it makes a difference.
Oh - also turn AFC frame rate to "Focus" (slows it slightly but not
noticeably), and turn Focus Lock to "off". This one's very
important. It introduces (when turned on) a delay in shifting focus
points if distance suddenly changes. I'm not sure about the D200,
but on the 2Hs it makes far more trouble than it can ever cure.
Turn it off, and the camera comes alive.
I already use Focus Priority, but according to the Nikonians article, focus lock just means that the cam will track your object once focus is locked by half press of shutter. I believe, 50 milliseconds is all it takes to refocus, and the D200 even accounts for this.
From Nikonians article:
Subject IS moving: Predictive Focus Tracking figures out how far the subject will move before the shutter fires. Once you’ve pressed the shutter button all the way down it moves the lens elements slightly to correspond to where the subject should be when the shutter fires a few milliseconds later. In other words, it focuses slightly in front of your subject so that the camera has time to move the mirror and get the shutter blades out of the way.
It takes 50 milliseconds for the camera to respond to pressing the shutter release. If you are shooting an Airshow, for instance, in 50 milliseconds a fast moving airplane can move enough to slightly change the focus area by the time the shutter opens.
If you press the shutter in one smooth motion all the way to shutter release, first autofocus occurs, then the mirror moves up and the shutter starts opening. That takes the previously mentioned 50 milliseconds. In the time it takes for the camera to respond to your shutter release press, the airplane has moved slightly, which just barely throws the autofocus off. The camera’s computer predicts where the airplane will be when the image is actually exposed, and adjusts the focus accordingly.
I appreciate your input and suggestions. This thread has helped me to analyze this problem, and the only common denominator I can think of is the fact that my subject has been much smaller in these head on or back on shots, since I am poised for a pan when the subjects get much closer, and only take the head on or back on shots as a fore- or afterthought. On Friday, I will experiment with zooming in, framing tight, for head ons, to see if this will make a difference.
Thanks, again.
I hope this helps
Regards
Ewen Cameron
Kent, UK
--
james
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