Andrew Reid wrote:No continuous changes during shooting, that's not what I said.
Your wording was ambiguous; quote: "I was shooting in low light and needed F2. Every time a bright highlight (however tiny) came into the frame like a candle or street light, the camera switched my aperture to F10."
It doesn't do the AE based on an average, it will simply read the brightest highlight in the frame and set it to that.
You might consider this a bug, or a feature. It is the same ETTR exposure strategy that Magic Lantern provides on Canon DSLRs. It differs very much from traditional video exposure where you expose for the average because your dynamic range is limited to 8-10 stops. Instead, if your highlights are correctly exposed but the rest of your picture is 3 stops under, the 13 stops latitude still give you room in post to lift the underexposed part of the picture and gain a smooth highlight roll-off.
Conversely, when you have a dimly lit scene with no highlights, you overexpose (until the point where the image would clip) in order to maximize dynamic range; and you can still darken/crush the video in post.
It's a typical exposure strategy for a raw camera, and the one advocated/recommended for raw photography these days, too. It is my understanding that the BMPC switches to average exposure if you active the "Video" recording mode. In my book, this makes sense.
But I agree that it's bad that the camera doesn't memorize its exposure settings in between switching it off and on. The same goes for the focus peaking setting. Quite annoying that one needs to re-activate it each time the camera has been switched on again.