What is the cause of the "red ring" lens flare?

Question

I've been studying lens flares and the various phenomena that occur alongside the reflected "ghosts" that are most commonly associated with them. Of particular interest are the red rings that surround the light sources in shots like this one from ET:

And this shot from Blade Runner:

Can anyone explain what causes these rings, and what (if any) their proper name would be?

My theory is that they are some kind of diffusion effect, possibly caused by smoke being in the shot, as opposed to being a result of a physical property of the lens itself. It also seems to occur when the light source is pointing directly at the camera, with the size of the light source contributing to the softness.

As for the colour, they usually manifest as red, even if the light source appears to be completely white, as in this image from Apocalypse Now:

Any insights would be very helpful, thanks.

Answer 1

For me this looks like flare. And it is created by lens.

About the colour of first for me it's caused by the lens coating (each lens have different coating)

Answer 2

Flare -- All optical systems are debased by flare. This is stray light inside the camera that intermingles with the image forming light rays that comprise the image to be recorded. Stray light comes mainly from reflections off the polished glass surfaces of the various lenses that comprise the optical system. As the light rays from the subject passes by each optical surface about 5% will be reflected. Now a modern camera lens consists of many glass lens element. The light loss at each glass to glass or glass to air interface can reach 50% or more. These reflections generate misguided light rays. These are the mischief makers that generate artifacts with rings and streaks and ghost image. Additionally, the entire image is also bathed with misguided light rays. These rob the image of its contrast.

The light loss in optical systems was well studied by John Strutt, Nobel Laureate Physics and Optician James Taylor. They observed that old lenses on the shelf passed more light than new ones of the same design. Seems that England, during the industrial revolution, suffered from severe air quality for coal burning. Soot was deposited on lenses on the shelf. This was called “blooming”. Bloomed passes displayed less flare and produced brighter images.

Taylor experimented and devised ways to artificially bloom lenses by coating the glass with various thin layers of minerals. This is the process of coating lenses. A modern lens is likely multi-coated to handle unwanted reflections of various colors. Coating greatly reduces flare. A complex optical system that otherwise would lose 50% is greatly improved. However, flare still plagues us.

Answer 3

The color of lens flare, particularly rings, is dependent upon the color of the light causing the flare. Even though the light looks white because it's oversaturated¹ in the primary image of the light passing directly through the lens, the reflection is dimmer and thus colors are not shifted to white because they are not overexposed like the primary image of the direct light is.

It's also heavily influenced by the color of lens coatings.

In the end it's a combination of the color of the light, how bright the reflection is, and the color of the lens coatings on the surfaces doing the reflecting.

_{¹ For why oversaturated/overexposed colored light shifts towards white in exposed images, please see: Why is it that when the green channel clips, it turns into blue?}