Go for Boke

Go for Boke

To accurately create the bloom of highlights as they are
blurred requires 32 bit per channel color and source highlights
that are brighter than what would be called full white
in 8 or 16 bpc. The process of creating such an image is
explored and explained in Chapter 11.
The Lens Blur effect does not operate in 32 bpc—it instead
mimics the behavior of bright highlights through a lens.
It’s more or less a direct port from Photoshop; as such, it
can be slow and cumbersome in After Effects. It won’t blur
beyond 100 pixels, and the effect does not understand
non-square pixels (it creates a perfect circle every time).
Instead of 3D camera or layer data, Lens Blur can use a
Depth Map Layer, using pixel values (brightness) from
a specifi ed Depth Map Channel. You can rack focus by
adjusting Blur Focal Distance. Iris Shape defi nes polygons
around the highlights, corresponding to the number of
blades in the iris; these can also have a specifi ed Iris Blade
Curvature and Iris Rotation (this rotates the polygon).
The actual amount of blur is determined by Iris Radius,
the bloom by Specular Threshold (all pixels above this
value are highlights) and Specular Brightness, which
creates the simulation of highlight bloom. These are the
controls you’ll tweak most.
The Noise controls are designed to restore noise that
would be removed by the blur operation; they don’t relate
to the blur itself and can be ignored in favor of grain techniques
described in the following section.

By no means do the settings in Lens Blur (or for that
matter, third-party alternatives such as Lenscare from
Frischluft) exhaust the possibilities for how defocused
areas of an image might appear, especially when illuminated.
Keep looking at the reference and thinking of ways
to re-create what you see in it.