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With the Mark IV, In Manual mode you can set your specific shutter speed, Aperture, then use Auto ISO, then in Custom Settings go to Exposure, C.Fn1, number 16, Enable, Info change, then you dial in EV Compensation + or - 1 Stop using increments of1/8th of a stop! It will not show you have done this while looking through you view finder on your EV scale, but it does work.
That's not really EC, but exposure calibration if you find your exposure is a bit out. Also it's not something you can change on the fly. Too bad if you need to dial in +2EV compensation while shooting on snow say. You can get genuine EC in Av and Tv mode with Auto ISO.