All hue curves outer points are locked together

[davidh]

Is there any reason why the extreme points of the hue curves move always jointly and cannot be uncoupled in the Color Curves transformation? The curves behave the same way as in Monochrome where it make sense just to lighten or darken the corresponding hue pixels. In PWP7 they can be moved independently and therefore used to change hues.

[jsachs]

Yes, hue is really circular with the same pure red being present at both ends. To get the curves to work correctly, a point is fixed at either end and they move together. You can still change hues, but it is done by specifying a hue shift for each hue. The hue curves in PWP7 made it very hard not to create a kink in the hue curve at red.