The histogram for an image and the overexposure warning are meant (in theory) for objective verification of the image while shooting and adjustment of shooting parameters according to the indications in the preview window one can see the overexposed areas right away, and the histogram displays the overall distribution of tones on the shot.
The goal of this article is to elaborate on the procedure of juxtaposing the camera histogram and the real raw data, as opposed to merely provide settings and numbers. This, among other reasons, was why the shooting conditions were not exactly typical.
We used a 5D Mark II camera with a 2.0.9 firmware and at 200 ISO. For other cameras, different shooting conditions, possibly other ISOs, and other firmware, separate measurements are to be performed.