When light rays coming from a bright source(s) of light (such as the sun or artificial light) directly reach the front element of a camera lens, they can reflect and bounce off different lens elements, diaphragm and even off the sensor, potentially degrading image quality and creating unwanted objects in images. Better known as lens “flare”, the effect can impact images in a number of ways: it can drastically reduce image contrast by introducing haze in different colors, it can add circular or semi-circular halos or “ghosts” and even odd-shaped semi-transparent objects of various color intensities. Flare is not always undesirable in photography though – sometimes in is used creatively to add artistic elements to images. In fact, lens flare is often deliberately added to movies and computer games to add a sense of realism and boost the visual experience of the viewer.
To help decide whether to use flare in images, it is a good idea to understand why it happens in the first place. Let’s go over the causes of flare in detail, then discuss ways to use, reduce or perhaps completely avoid it.
1) What is Lens Flare?
Lens flare occurs when a point of light source such as the sun is much brighter than the rest of the scene, and it either happens to be in the image (within lens angle of view), or simply hits the front element of a lens without being present in the image. Depending on the position of this bright light source, it can result in a lot of haze / lack of contrast, orbs and polygon artifacts scattered throughout the image, semi-round shapes with rainbow colors, or a combination of all of the above. This happens due to internal reflections that take place inside the lens and even between the imaging sensor and the lens (more on that below). Take a look at the below illustration: