Gaussian-based glow is the most common way to diffuse light. It provides for a smooth output that feels natural to the viewer.
Box-based glow produces details with square shapes. The output has more contrast than when produced via Gaussian.
Disc-based glow produces details with round shapes. The output has more contrast than when produced via Gaussian.
Zoom-based glow simulates motion blurring anchored to a point. The output has rays radiating outward from the chosen origin. The Contrast parameter determines whether rays are more or less visible in the output.
Directional glow simulates motion blurring along a fixed direction, specified through a separate Angle.
Bokeh is a variant of Disc that produces non-uniform details, i.e. ring shapes that simulate lens effects. The Contrast parameter allows you to control the visibility of ring edges.
Variable applies a Gaussian-based glow in various amounts, according to the current mask. Variable blur is possible only when using a custom Source or Mask.