sigma:this controls the center region of the tonality, i.e. it determines what are mid tones  and what are extremal values. increasing sigma will make more pixels be considered as mid tones.  this can be useful if you mainly care about contrast in the image. it will make the :clarity:slider more powerful. decreasing :sigma:will remove from the area where :clarity:has a big effect  and instead consider a larger range of pixels as *shadows* or *highlights*, giving more power  to the corresponding sliders.
shadows:this setting is used to control the shadows of the image. pulling shadows to 0 means  shadows will disappear. increasing the shadow value will pull more pixels into the shadows.
hilights:this is similar but for highlights. use it to control the sharpness of your  speculars.
clarity:this controls the amount of local contrast. it can also be used to smooth the image  if you dial in a negative number.
