What section of the color chart is used to calibrate brightness?

The section with the grayscale bars (bottom row, from white to black)

Brightness calibration is typically done using the grayscale section of a color chart. The grayscale bars provide a range of luminance levels from white to black, allowing the calibration process to adjust the display so that each shade is distinct and accurately represented. Proper calibration ensures that the display shows details in both bright and dark areas of the image, achieving the correct overall brightness.