Chromatic Aberration

Chromatic Aberration

Even further down the road of questionably aesthetic visual
phenomena is chromatic aberration, a fringing or smearing
of light that occurs when a lens cannot focus various
colors on the spectrum to a single point, because of the
differing wavelengths. The effect is similar to that of light
passing through a prism and dispersing into a rainbow of
colors.
Like vignettes, and optically related to lens fl ares and boke,
chromatic aberration is something higher-end lenses are
designed to avoid, yet it can occur even under relatively
expensive and high-end shooting circumstances, particularly
if there is any type of lens conversion happening.
Unlike the others, it can really look like a mistake, so it’s
not the kind of thing you would probably add to a clip
in order to make it look cool; instead you might add it to
a shot or element to match another shot or background
plate in which it appears. My recommendation in such
a case?
1. Duplicate the layer twice and precompose all three.
2. Use the Shift Channels effect to leave only red, green
or blue on for each layer (so you end up with one of
each).
3. Set the top two layers to Add mode.

4. Scale the green channel to roughly 101% and the blue
channel to roughly 102%.
5. Add a small amount of Radial Blur (set to Zoom, not
the default Spin).
A before and after comparison.