Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 522

Glow effect
The Glow effect finds the brighter parts of an image and then brightens those and surrounding pixels to create a
diffuse, glowing aura. The Glow effect can also simulate overexposure of brightly lit objects. You can base the glow
on either the original colors of the image or on its alpha channel. Glows based on alpha channels produce diffuse
brightness only at the edges of the image, between the opaque and transparent regions. You can also use the Glow
effect to create a gradient glow between two colors (A and B colors) and to create multicolor effects with looping.
Rendering the Glow effect at Best quality can change the appearance of the layer. This change is especially true if you
use Adobe Photoshop arbitrary maps to color the glows. Be sure to preview at Best quality before you render the
effect.
Glows tend to be brighter and more realistic in 32-bpc projects. Consider working in 32-bpc color for this reason,
even if footage items don't contain high–dynamic range color values.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Original (left), and with effect applied (right)
Determines whether glow is based on color values or transparency values.
Glow Based On
Sets a threshold as a percentage brightness to which the glow isn't applied. A lower percentage
Glow Threshold
produces more glow; a higher percentage produces less.
The distance, in pixels, that the glow extends out from the bright areas of the image. Larger values
Glow Radius
produce diffuse glows; smaller values produce glows with sharp edges.
The brightness of the glow.
Glow Intensity
Specifies how to composite the effect results with the layer. On Top places the glow on top of the
Composite Original
image, using the blending method selected for Glow Operation. Behind places the glow behind the image, creating
a backlighting result. None separates the glow from the image.
To reduce the layer to the glow only, choose None for Composite Original and None for Glow Operation. To achieve
a glow effect for text that knocks out (blocks) all layers below it, choose Silhouette Alpha for Glow Operation. These
glow effects are more noticeable if the image has a feathered edge.
The colors of the glow. A & B Colors creates a gradient glow using the colors specified by Color A and
Glow Colors
Color B controls.
The shape of the gradient curve to use if A & B Colors is selected for Glow Colors.
Color Looping
Creates multicolor ringing in the glow, if you select two or more loops. A single loop cycles through the
Color Loops
gradient (or arbitrary map) specified for Glow Colors.
Where in the color cycle to begin color loops. By default, color loops begin at the origin of the first loop.
Color Phase
The midpoint specifies the balance between the two colors used in the gradient. Lower percentages
A & B Midpoint
use less of the A color. Higher percentages use less of the B color.
The color of the glow if you choose A & B Colors for Glow Colors.
Color A, Color B
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