Question - In Profiler when setting GCR manually how is the GCR% slider different than the %k axis on the curve.
Answer - These two controls, while both impacting the black separation, really serve very different purposes. The "Black Curve" control allows you to define the maximum amount of black that can be used for any given point in an image based upon each point's L* value. For example, select the "offset" preset. With this default curve selected there would be no black in any value with an L* value of 50 or higher. A point in an image with L* value of 20, could have as much as 32% black. This does not mean it will have 32% black, but it will have no more than 32% black. This control is used to define the maximum amount of black. The GCR slider controls the percent of gray component that will be replaced with black. If you wish to replace the entire gray component with black you should slide the slider all the way to the right. If you wish to maintain some level of CMY, position the slider someplace along the continuum. For example if you set the slider at 50%, only half the gray component will be replaced with black, the remaining 50% will be composed of CMY. In case of conflict, the black curve has dominance. Also note that checking the "Intelligent Black" check box can override either control. This is designed to protect you from making choices that drastically limit your gamut. For example, you could pull the black curve all the way to the lower left hand corner, which means that in effect there would be no black at all used in the separation. Checking Intelligent Black will add black back in where the software deems it appropriate. Of course you can simply uncheck this box to maintain full control.