In PhotoLine there are many ways to convert an image to gray: Hue/Saturation, False Color, Convert Layer Type, the Channel Mixer, ...
The Gray Mixer is one more way: here you can assign a weight to every color. A value of 0% means, that this color has the standard weight. If every color is set to 0%, the result will look like Convert Layer Type. The value of the Gray Mixer lies in strengthening or weakening single colors and thus raising or reducing their contrast in the resulting gray image.