The Luminance Tone Curve allows you separate control over adjustments than the RGB composite control.
When correcting tone with by using the general RGB composite tone curve, both color and brightness will also change. Because you can adjust only the tone of brightness with the L Tone Curve channel, color omissions decrease, and you have fewer color shift issues that arise in chroma. as well as changed in chroma.
While both portrait or macro photography can contain a lot of blur, you can achieve both soft and vivid expression using this new channel.
High Key Adjustments
High Contrast Adjustments
Luminance Tone Curve Control
The Tone Curve control is a tool for making minute adjustments to tone expression after completing adjustments to other biases and for converting brightness for effect