from me looking at it the first column of numbers of the max value of that color range & the next four are how bright you want all the other color ranges + alpha, but in that row's color range. so if you have Red = 1 & then in the same row blue = .5, it makes all the rights as bright as the original image PLUS adds in the brightness of the blues to the reds.

neat little thing, never looked at it before now.

channel blend gives you access to the scale factors in the algorithm used to calculate the luma value from the RGB values. I think it's mainly a tool for the color technologists who have the need for color space remapping.

I'll dig into the Technicolor example, didn't realise Matthew had provided the presets.
I've tried using it to emulate various B&W looks, although I could have done the same thing with curves and the B&W FX.

Bill, what you're saying is what I'm thinking but working out all those values is what escapes me and it's not friendly enough to just push things around and observe what happens.

Bob.

channel blend gives you access to the scale factors in the algorithm used to calculate the luma value from the RGB values. I think it's mainly a tool for the color technologists who have the need for color space remapping.
That's an interesting way of putting it! :D You could use the channel blend filter to do some algebra equations (e.g. matrices). All the various Y'CbCr <--> R'G'B' conversions are algebra... you can concatenate the equations together into a matrix, which you can stick into the channel blend.

I don't think the original intention was for color space conversions (as in fixing luma co-efficients being decoded incorrectly). Just look at the presets.

2- What I find it useful for is when converting values to black and white.

You can make up presets so that you only convert R / G / B
and R + G / G + B / R + B channels into black & white.