Separating digital negatives in shadows/midtowns/highlights for richer prints

Thanks, Bob. That makes sense.

Regrading the blendif layer. Each of the sliders (left and right) can be split. If you do not split there is a hard edge between the shadows and the rest or the highlights and rest as the case may be. To split the sliders, hold alt key and then move half of the slider to define an fuzzy zone so the transition is smooth.

Of course if you like to use masks, the exact same thing can be done by going to Select> Color Range > Shadows or Highlights and specifying the range and the fuzziness more precisely.

:Niranjan.