Canon MARK IV User Manual (en)

: Program AE
Take the picture.
Compose the shot and press the 
shutter button completely.
If the “30"” shutter speed and the maximum 
aperture blink, it indicates underexposure.
Increase the ISO speed or use flash.
If the “8000” shutter speed and the minimum 
aperture blink, it indicates overexposure.
Lower the ISO speed or use an ND filter (sold 
separately) to reduce the amount of light entering 
the lens.
During automatic AF point selection (p.97) or manual AF point selection with 
expanded AF points (p.222), multiple AF points might light up 
About Program Shift
In the Program AE mode, you can freely change the shutter speed and 
aperture combination (Program) set automatically by the camera while 
maintaining the same exposure. This is called Program shift.
To do this, press the shutter button down halfway, then turn the <6> 
dial until the desired shutter speed or aperture value is displayed.
Program shift is canceled automatically after the picture is taken.
Program shift is not possible with flash.