Trapcode Starglow

Pre-Process

The pre-process section lets you set a threshold for controlling where the Starglow effect appears, and lets you use a built-in circular mask to restrict the glow area.

Threshold

Threshold defines the minimum level for the highlights. A low value will give more glow in the image, and a high value will make only the very bright areas glow. The images below show Starglow output using a shot of the sun on water with different Threshold values.

source
Source
thresh_hi
High Threshold

thresh_lo
Low Threshold

Threshold Soft: This controls the softness of the border between lowlights and highlights.

Use Mask: Check this to enable the internal circular mask.

Mask Radius: This control sets the size of the internal circular mask in pixels.

Mask Feather: The Mask Feather value sets the softness of the internal circular mask.

Mask Position: Define the center point of the circular mask with this control.