Frustration Station: low light action in changing light

I shot a performance by the Robinson Ballet last week and it was challenging to say the least. I was at ISO 6400 for most of the performance and at times as slow as 1/60 sec and F2.8.
When the focus hits and the exposure is good, I am blown away by the Mark IV. I know the D3s is the king of low light but the Mark IV is so much better than anything I have used prior.
Here are a couple of shots from the night


Camera Maker: Canon
Camera Model: Canon EOS-1D Mark IV
Lens: EF300mm f/2.8L IS USM
Focal Length: 300.0mm
Aperture: f/2.8
Exposure Time: 1/500
ISO equiv: 6400
Metering Mode: Spot
Exposure: aperture priority
White Balance: Auto

click on image to go to flickr and see it bigger


and another at ISO 6400 1/60


Now with that being said, I missed a lot of images. I could blame the camera but...we all know better. There are two main issues with event shooting in low and constantly changing light that I struggle with:
focus
proper exposure

Focus is tricky even with the top of the line body and high end lens in front of it. What I do to maximize my keeper is:

1. put the focus point control on the joystick on the rear of the camera. Either that or get very good at quickly changing focus points without taking your eye off the viewfinder. This is crucial for number 2

2. If you are shooting with enough DOF this works: While maintaining the composition that you want for the image, move the focal point around to match up with the part of the image that has the highest contrast. It may be a sequined belt or a headband with bright material. If you simply focus on the face because that is what you want in focus, even if it is shadowed or lacking any contrast, the lens will likely start hunting and you will miss shots.

3. If you are shooting really wide apertures and are so close that your DOF is really thin, then number 2 may not work as well and you need to keep your focus point on your desired area. If you are lucky enough to have a high contrast item in the same focal plane of the face, then you can still use number 2. For example if a belt buckle is a great target to acquire focus and the person is relatively upright, then the face will be in nearly the same focal plane.

You really need to figure out how well your camera's focus works. My 1D III was fantastic at locking focus in low light..perhaps a bit better than the mark IV. My 40D was horrible in comparison. Remember that the lens in front of the camera is a big part of the equation. A fast aperture, high end lens has a better motor and bigger aperture to focus through.

Some cameras are also much better with the center point focus in comparison to outer rings. My Mark IV can focus as well with the outer rings if I use a 2.8 or faster lens. Make sure you read your manual to find out how your body lens combo performs.

Exposure:

I still am not sure what the best approach is for rapidly changing and highly focused light. It is either AV or Manual and at times I swear one is better than the other.

Stay tuned...it is late and I will finish up in a couple of days.