AI servo focus at night

Hey all,
been off of here for forever, but anyway I've got a 7d and I do stage rally photography. I've been able to set up off camera flashes to fire on the cars as they drive by, snooted/bounced so the light doesn't go above the mid door of the cars (keeps light out of the cockpit), my only problem is, getting the cars in focus. Is there a good IR focus assist that still has a hotshoe available for my wireless triggers and works well with AI servo. Can't use standard flash assist to focus since it's usually a bad idea to blind drivers.


Thanks all
~Jordan

Traditional focus assist (the red beam from a Speedlite or the strobing from a popup or smaller flash) doesn't work with AI Servo mode. If you want more light for focusing, you need to add light. Note that the focus assist is red light, not IR - IR would not help you focus (or if it did, your focus would be off anyway, beacause of the longer wavelength).

I shot a wedding three years ago with a 7D and a 1D Mark III. As the night wore on, the pavillion was lit with just some strings of 7W nightlight bulbs on strings (glorified Christmas tree lights), plus the DJ's four-color lights on a stand. The 7D really struggled, while the 1D3 didn't care in the least. I suspect you're running into the limits of the 7D systems.

That said, I agree with neuroanatomist's suggestion to add light.