Lens Flare: What Is It And How Do You Prevent It?
by Bob Shell

Lens flare is one of those optical phenomena which can ruin an otherwise perfect photograph, and all too often you don’t know it until after the fact when you get your photos back from processing. Lens flare can show up as yellow-orange streaks, geometrically shaped spots, or an overall haze which reduces contrast and saturation and masks subject detail.

Lens flare, also called veiling glare, is caused by light reflecting inside the lens, either from lens surfaces or from internal components in the lens. At every lens surface where the lens meets air a certain amount of light will be reflected. Modern lens coatings have reduced the amount of this reflection, but none can eliminate it.

The more air/glass interfaces a lens contains, the more light will potentially be reflected and cause problems in your photos. Modern zoom lenses often contain a large number of individual lenses (lens elements) inside their barrels.

When you look at lens specifications you will usually see something labeled “Elements/Groups” followed by a number like 18/10.

This means that this particular lens has 18 separate lens elements in its barrel, but some are cemented together into groups. The number of air/glass interfaces capable of causing lens flare is normally the number of groups doubled, so this hypothetical lens would have 20 air/glass interfaces and would likely be prone to lens flare.

Problem causing flare is usually caused by very bright lights within the image area, such as the sun in the sky, or just outside the image area.

Typically it is the lights just outside the image area, those you don’t see when composing your image, which cause the problems. Contrary to what some people believe, there is no filter which will correct for lens flare. In fact, by adding two more air/glass surfaces, a filter may simply make matters worse.

The solution for lens flare is a properly designed lens hood. I personally believe that no lens should ever be used without a proper lens hood, and some manufacturers apparently agree and include good lens hoods with their lenses.

For those lenses which do not come with hoods, most manufacturers offer lens hoods specifically designed for the lens as accessories, and generic hoods are available in those cases in which the manufacturer does not offer them.

For very serious professional photography the manufacturer’s lens hood is often replaced with a bellows type lens hood sometimes called a compendium. These are standard equipment in the motion picture industry and are also available for use with most still cameras.

Their advantage is that they can be adjusted to exactly match the focal length of the lens in use for maximum blocking of extraneous light. Although somewhat large and inconvenient for use in 35mm cameras in the field, I consider them essential equipment for my medium format cameras in my studio.