I would think randomizing the strobing would be effective as well. All of this defeating of auto exposure adjustments makes me think back to the days of Macrovision and how easily it could be defeated as it was not randomized at all. Then again, it was also easily just stripped out of the signal.
With random timing, you're more likely to get one period that's long enough for the auto-exposure to correct it and see the face. Autoexposure takes time because it has to use a feedback loop to search for the correct exposure, so if the brightness changes fast enough, it can't keep up.
you set a maximum on period so that doesn't happen. if you develop something with a known pattern, that can be programed in to be countered. hence my example of Macrovision. randomizing the values means it is much harder to counter.
