ETTR when HDMI connected

[garry23]

I'm giving a talk at my local club on ML and will be projecting from my 5DII via an HDMI cable.

Just tried it out, and ignoring the few seconds to initially sync, I have noticed a strange thing.

With the HDMI cable out ETTR works as it should. With the cable in it always gives to 1/8000 and says exposure limits reached.

Has anyone else observed this behavior? It is not an issue for me, as I don't shoot with an HDMI cable attached.