Hello. I have a quick question. When I had my Canon 6D, I purchased a head crop sensor that went in my camera so my viewfinder would show a cropping ratio (I photograph a lot of school kids). Does anybody know if there is a setting or a tool for the R6 so I can have head cropping ratio in the camera? Thank you
"Canon 6D, I purchased a head crop sensor"
If you were focusing through the optical viewfinder (i.e. eyepiece) then what you are referencing was most likely a custom focusing screen.
The R6 shows exactly what the sensor sees. You can select various aspect ratios to show on the LCD and in the viewfinder.