Anamorphic Lens
An anamorphic lens squeezes a wide view onto a narrower frame, then gets stretched back. It explains widescreen cinema, oval bokeh and long blue flare streaks.
What is an anamorphic lens?
An anamorphic lens magnifies the picture more in one direction than the other, usually squeezing a wide scene sideways so it fits on a narrower piece of film or sensor. A matching lens on the projector, or a setting in the editing software, stretches it back to full width.
The squeeze comes from cylindrical glass, which bends light along one axis only, like a slice of a drinking straw. Ordinary lenses are round in every direction. A 2x anamorphic lens takes in twice the width a spherical lens of the same height would, which is how a nearly square 35mm frame turned into a cinema screen more than twice as wide as it is tall.
Where widescreen came from
The French astronomer Henri Chrétien built the first practical cinema version, the Hypergonar, in 1927, the year Abel Gance needed three cameras side by side to shoot the wide finale of Napoléon. Chrétien's lens did it with one camera, yet the studios showed little interest for the next 25 years.
Then television started emptying cinemas. In 1953 Twentieth Century Fox bought Chrétien's lenses and released The Robe in CinemaScope, the first feature in the process. The frame started out at 2.55:1, and once optical soundtracks took back some space the standard settled at 2.35:1 and later 2.39:1, which is still what people mean by scope today.
How do you recognize anamorphic footage?
Look at the out-of-focus lights. A spherical lens turns them into round discs, while an anamorphic lens with the squeeze at the front stretches them into tall ovals once the picture is unsqueezed. Look at the edges of the frame too, where straight lines often bow a little and focus falls off unevenly.
The flares are the giveaway everyone knows. A bright light inside or near the frame throws a long, thin horizontal line, because the cylindrical elements spread the stray light along one axis only. Many vintage lenses have coatings that tint the streak blue, and that blue line became so linked with science fiction that films shot on spherical lenses fake it in post.
Widescreen alone doesn't prove anything. Most 2.39:1 films and videos today are simply cropped from a taller frame, and they show round bokeh and no streaks at all.
Squeeze factors you'll see
Classic cinema anamorphics squeeze by 2x, sized for the 4:3-shaped 35mm frame. Lenses built for today's wide 16:9 sensors often squeeze by 1.33x or 1.5x, since a 16:9 frame stretched by 1.33 comes out at roughly 2.37:1. Phone clip-on lenses are usually 1.33x for the same reason.
Getting the streak without the lens
Anamorphic Lens Flare stretches every pixel above a brightness threshold into a horizontal line. Night scenes work best. On a bright daytime frame, set Threshold near 0.8 so only the sun and hard reflections streak, and keep the Anamorphic preset's pale blue Tint for the classic look or switch to Warm for tungsten street lights.
