Color and Mastering for Digital Cinema

4Transfer Function

An important characteristic of any digital imaging system is the transfer function that defines the relationship between its code values and the displayed picture. This chapter will review the background that led to the specification of a non-linear encoding transfer function for digital cinema distribution that is based on a power law with a gamma of 1/2.6.

The CIE XYZ tristimulus values are calculated with a normalizing constant (52.37) that sets the Y tristimulus value equal to the relative luminance in cd/m² above black, and both the X and Z values are multiplied by the same constant. With this specification of the color, the following equations define the encoding transfer function where X, Y, Z are the tristimulus values ...