I always use this setting for start,
Hue; 50
saturation ; 47
brightness; 47
color range; 220-230
fall off; 990
see what showed up and play with brigtness and saturation. If background is white or shiny, push up the brightness, and pull downside the saturation, if background is colorful must be the saturation up and brightness down.
At last try fall off upwards max 997, if need it,