For example: What contributes to this streaking? Why doesn't spherical lenses have this effect? How is it used in photography?
Some lenses give really harsh and unwanted flares. Some gives beautiful flares that add depth to an image. What's the science behind this?
I heard a couple of years ago that only certain types of lens caused flare to appear, something related with the material and/or quality of the lens. Is this true? Which material/quality caused flare? ...