What coefficients does Krita use for YUV/YCbCr?

[Matthew Woehlke]

I don't know if anyone follows k-c-d, but I'm working on a color 
blending function for kdelibs that will support HSY color space (like 
HSL but with luma as in YUV/YCbCr color spaces). Alas, there are two 
common sets of coefficients used to calculate Y:

601: Y' = 0.299  R' + 0.587  G' + 0.114  B'
709: Y' = 0.2126 R' + 0.7152 G' + 0.0722 B'

I figure this is probably the best place to ask; which would be better 
to use in kdelibs (or should I offer /both/)? Which does Krita use?

-- 
Matthew
"I can hear you / just barely hear you / I can just barely hear you"
   -- "I Can Hear You", by They Might Be Giants