#define SF_COLOR_LUM_BLUE 0.0820
The SF_COLOR_LUM_[component] define the floating point luminance vector values for red, green, and blue. To convert colors into black and white, the balance red, green, and blue coefficient of 0.3086, 0.6094, and 0.0820, respectively, is used. Here, the Blue luminance floating point vector value 0.0820 is used.
The standard NTSC weights of 0.299, 0.587, and 0.114 are NOT used, as they are only applicable to RGB colors in a gamma 2.2 color space.
Render_Color.h