The tone value is the amount of black & white levels that a coloured image contains. Tonal Correction is done with the help of the colour or grayscale specifications (these are given in percent), which are within a specified colour or grayscale spectrum. 100 percent corresponds to maximum darkness or colour coverage and 0 percent is transparency. With a tonal value correction you can expand or limit the tonal range. The brightness and contrast can also be adjusted.