Why do anamorphic lenses create horizontal flare streaks?
Asked 9/7/2013
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Anamorphic footage often shows bright light sources producing long horizontal flare streaks. What in an anamorphic lens causes this effect, and why is it different from the flare you usually see with spherical lenses? Also, how is this look typically used in photography or cinematography?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
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Spherical lenses tend to have spherical distortion and reflected light patterns. They are circular and symmetrical.
Anamorphic lenses have a built-in "squeeze ratio" that compresses the horizontal axis of the image during image capture. Unfolding the squeezed image for viewing stretches the distortions or internal reflections, from inside the lens barrel, horizontally. When the angle is right, flare that would be circular becomes a horizontal line parallel to the distorted anamorphic horizontal axis.
Over-saturation of the image sensor can also produce linear picture artifacts. Depending on the "polling" of the chip, the lines can be horizontal or vertical. They can appear white or black according to the type and design of the sensor chip. These tend to be the same width across the entire image unlike your example, here.
EDIT: I don't mean to be flip; but, any effect can be used to advantage if the effect is relevant to the subject or to the image content. Using an effect creatively can heighten the emotion of the shot relative to one without such an image treatment.
I'm curious about the symmetric arrangement of the 5 light spots in a "vee" around the highlight. Fascinating.
Originally by user21789. Source · Licensed CC BY-SA 4.0
user21789
12y ago
0
Generated from our catalog & community — verify before relying on it.
Anamorphic lenses optically squeeze the image in one direction (typically horizontally) so it can be unsqueezed later. Because the lens is not symmetrical like a normal spherical lens, internal reflections and flare are also stretched along that axis. A flare that might appear more round or compact in a spherical lens can become a long horizontal streak after the anamorphic image is expanded for viewing.
Spherical lenses are generally rotationally symmetric, so their flare patterns tend to stay more circular, polygonal, or evenly shaped rather than forming a strong directional line.
In many examples, you may also see additional repeated bright spots or shapes. Those are often separate internal reflections bouncing between lens elements or filters, not the main anamorphic streak itself.
This effect is mainly used as a stylistic choice, especially in cinematography, to give bright practical lights, headlights, or the sun a dramatic “cinematic” look. Similar linear artifacts can also come from sensor overload in some situations, but the classic blue horizontal streak is associated with anamorphic lens flare.
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