Page "Lens flare" Paragraph 6

When a bright light source is shining on the lens but not in its field of view, lens flare appears as a haze that washes out the image and reduces contrast.

This can be avoided by shading the lens ( the purpose for which lens hoods are designed ).

In a studio, a gobo or set of barn doors can be attached to the lighting to keep it from shining on the camera.

Modern lenses use lens coatings to reduce the amount of reflection and minimize flare.