Glow effect
The Glow effect finds the brighter parts of an image
and then brightens those pixels 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, because the high dynamic range in a 32-bpc project
prevents the color values of the glow from being clipped. Consider
working in 32-bpc color for this reason, even if footage items don’t contain
high–dynamic range color values.
Chris Meyer provides a basic overview of the parameters of the
Glow effect in a video tutorial on the Lynda.com website.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Original (left), and with effect applied (right)
- Glow Based On
- Determines whether glow is based on color values or transparency
values.
- Glow Threshold
- Sets a threshold as a percentage brightness to which the
glow isn’t applied. A lower percentage produces glow on more of
the image; a higher percentage produces glow on less of the image.
- Glow Radius
- The distance, in pixels, that the glow extends out from the
bright areas of the image. Larger values produce diffuse glows;
smaller values produce glows with sharp edges.
- Glow Intensity
- The brightness of the glow.
- Composite Original
- Specifies how to composite the effect results with the layer.
On Top places the glow on top of the 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.
- Glow Colors
- The colors of the glow. A & B Colors creates a gradient
glow using the colors specified by Color A and Color B controls.
- Color Looping
- The shape of the gradient curve to use if A & B Colors
is selected for Glow Colors.
- Color Loops
- Creates multicolor ringing in the glow, if you select two
or more loops. A single loop cycles through the gradient (or arbitrary
map) specified for Glow Colors.
Note: You can create an arbitrary
map (.amp) file by applying the Curves effect, selecting the pencil
icon, then clicking the save (floppy disk) icon. Use an arbitrary map
file in the Glow effect by clicking the Options link, then selecting
the .amp file.
- Color Phase
- Where in the color cycle to begin color loops. By default,
color loops begin at the origin of the first loop.
- A & B Midpoint
- The midpoint specifies the balance between the two colors used
in the gradient. Lower percentages use less of the A color. Higher percentages
use less of the B color.
- Color A, Color B
- The color of the glow if you choose A & B Colors for
Glow Colors.
- Glow Dimensions
- Specifies whether the glow is horizontal, vertical, or both.
