Lightness Channel in Photoshop

[wmaburnett]

I am reading a photoshop tutorial and it sais to clock highlight in the lightness channel.... I cannot find the lightness channel or where to click highlight , could somebody lend some assistance to point me to where it is?
Thanks!
~William

[big pix]

Lightness channel is in LAB colour.........

in photoshop go> image>mode>lab color

then go> Layer>new ajustment layer>curves> a new box opens for new layer asking for a name, just hit OK........

this will open up your lightness channel, and A & B ajustments for lab color........

[wmaburnett]

Thanks!