Parts of a flare

A real lens flare is the combination of several physical phenomena, which have to be modeled individually for photorealistic rendering.

Real lens flare A real lens flare with the central flare and several ghosts visible

The two main parts of a lens flare are the central flare and the ghosts.

The central flare is the starburst pattern that is covering the light source, which is surrounded by the ghosts.

Ghosts

Because the ghosts are highly dependent on the exact construction of the lens, it is basically impossible to generate a perfect replica of a real lens flare unless the lens design is known. This is why the Flares Science main application ships with several lens prescriptions.

Ghosts Ghosts generated by Flares Science Polyflare. Notice the subtle chromatic aberration

Central flare

The central flare however is only dependent on the aperture shape, which is significantly easier to find out for any given lens.

Central flare Central flare generated by Flares Science Starburst