What causes auto ISO to lock at ISO400? Andy Wilson, Market Harborough

Brian says… There are two possible causes, the most likely is that you used a Speedlite or raised the built-in flash – this almost always switches the ISO to 400, sometimes a little higher. Or your camera is set to limit the range of auto ISO and you have a limit of ISO400.

I have CF and SD cards in my EOS 5D Mark IV, and record to both together, which card does the Camera Connect app read from?