Here's a breakdown of how they work:
1. Squeezing (At the Time of Recording):
* The Primary Function: Anamorphic lenses use a special optical element, typically cylindrical lenses (lenses curved only in one direction), to compress the image horizontally. Imagine taking a wide panorama and squeezing it together like an accordion. This compression factor is called the "squeeze ratio" (e.g., 2x anamorphic squeezes the image by a factor of 2 horizontally).
* How Cylindrical Lenses Work: Unlike spherical lenses that focus light uniformly in all directions, cylindrical lenses only focus light along one axis. They compress the image horizontally while leaving the vertical dimension untouched. This is the key to the anamorphic "squeeze."
* Benefits of Squeezing:
* Wider Aspect Ratio: By squeezing the image, the anamorphic lens effectively makes the image wider than the native aspect ratio of the film or sensor. When unsqueezed, it creates a wider, more cinematic aspect ratio.
* Efficient Use of Sensor/Film Area: Instead of cropping the image to achieve a widescreen aspect ratio (which throws away vertical resolution), the anamorphic lens uses the entire area of the sensor/film to capture the information, resulting in a sharper, more detailed widescreen image.
2. Un-Squeezing (During Projection or Post-Processing):
* The Reverse Process: The squeezed image recorded by the anamorphic lens looks distorted. To correct this, the image needs to be "unsqueezed" back to its proper proportions.
* Two Methods:
* Projection (Traditionally): In film projection, a similar anamorphic lens (or a digitally processed equivalent) is used to unsqueeze the image and project it onto the screen with the correct aspect ratio.
* Post-Processing (Modern Digital Workflow): In modern digital filmmaking, the footage shot with anamorphic lenses is unsqueezed digitally in post-production software (like Premiere Pro, DaVinci Resolve, Avid Media Composer, etc.). The software simply stretches the image horizontally by the squeeze ratio (e.g., 2x).
Key Characteristics & Effects of Anamorphic Lenses:
Beyond the wider aspect ratio, anamorphic lenses are often associated with a specific aesthetic, largely due to their optical characteristics:
* Oval Bokeh: Out-of-focus highlights (bokeh) become elongated into oval shapes instead of the round shapes produced by spherical lenses. This is a signature anamorphic look.
* Horizontal Lens Flares: Anamorphic lenses are prone to creating long, horizontal lens flares (sometimes called "streaks"). These flares occur when bright light sources hit the lens. Many filmmakers embrace this effect, making it a characteristic of the anamorphic look.
* Falloff: Slight image softness, especially near the edges, can be more pronounced with anamorphic lenses.
* Distortion: Anamorphic lenses can introduce some unique distortion characteristics, though modern designs minimize these.
In summary:
Anamorphic lenses are sophisticated optical tools that allow filmmakers to capture a wider, more cinematic image. They work by horizontally squeezing the image onto the sensor/film and then unsqueezing it during projection or post-production. Beyond the wider aspect ratio, they also create unique optical effects like oval bokeh and horizontal lens flares, contributing to the "anamorphic look" that is often associated with a classic cinematic feel.