Often, you want to balance light intensity between two areas within a scene. This is important outdoors to allow more sky detail while properly exposing the foreground. Exposing for the foreground will produce a washed-out, over-exposed sky, exposing for the sky will leave the foreground dark, underexposed.

* Part clear, part neutral density, with a smoothly graded transition between
* A Color-Grad ND.6-to-clear is often best for balancing sky to foreground
* Neutral gray appearance drops exposure