GreyScale

Converts the input clip to greyscale (no color), without changing the color format.

UK (Greyscale) and US (Grayscale) spellings are both allowed.

Greyscale(clip clip [, string matrix])
Grayscale(clip clip [, string matrix])

string  matrix = "Rec601"

In RGB based formats, the conversion produces the luma using the coefficients given in the matrix parameter.

• "Rec601" : Use Rec.601 coefficients (and keeping luma range unchanged)
• "Rec709" : Use Rec.709 coefficients (and keeping luma range unchanged)
• "AVERAGE" : Use averaged coefficients (Y = (R + G + B) / 3)

If clip is YUV, the chroma channels are simply set to grey (128) – matrix is not used and must not be specified otherwise an error will be thrown.

See Color conversions for an explanation of the coefficients. Broadly speaking though,

• using Rec709, green contributes more to the output, compared to the default Rec601;
• using Average, blue contributes more.

In all cases, Luma range is not changed (0-255 in → 0-255 out; 16-235 in → 16-235 out)