The aim of display calibration is to measure and/or adjust the color response of a device (input or output) to a known state. In International Color Consortium (ICC) terms, this is the basis for an additional color characterization of the device and later profiling.
I am using the Spyder4pro to calibrate my MacBook pro retina display and it asks what my display's gamut and backlight are. Choices for gamut are: Unknown, Normal, and Wide. Choices for backlight ...