Aspheric Lenses Enabling High-Quality Video Streaming

Whether it is the latest show on Netflix^®, viral videos on YouTube^®, or classics on Disney+^®, the world is hungrier than ever for video streaming. This voracious consumption of video content is putting a serious strain on our internet bandwidth and networks are struggling to keep up. Cinematographers are cleverly shooting video with a shallow depth of field to improve the compression and streamed quality of video, but this requires specialized cinema lenses. High-end aspheric lens elements inside of these cinema lenses are indispensable for maintaining quality with a shallow depth of field, ultimately resulting in an optimal Netflix binging experience for people across the globe.

What is a Cinema Lens?

Cinema, or cine, lenses are specially-designed lens assemblies tailored for the demanding video quality requirements of filmmaking. They tend to be much larger and more expensive than the lens assemblies used for machine vision or commercial photography.

Saving 10% of Bandwidth by Using a Shallow Depth of Field¹

The demand for high-quality video has never been higher. The worldwide video streaming market reached USD 42.6 billion in 2019 and is experiencing explosive growth, with an expected compound annual growth rate (CAGR) of 20.4% from 2020 to 2027.²

Cinematographers have been cleverly creating content tailored for streaming by shooting with a shallow depth of field (DOF), which is the distance between the closest and furthest points at which an object will maintain a certain level of resolution without refocusing (Figure 1). A shallow depth of field means that only the shot’s main point of interest will be in focus while the background is blurry. This is often used to draw the viewer’s attention to something in a shot, but it is also advantageous for compressing and streaming video.

Figure 1: A “fast” lens with a low f/# results in a small DOF where objects are in focus.

Video files are quite large and must be compressed for streaming to reduce file size. Compression algorithms intelligently encode only the information that changes from frame to frame rather than every single pixel in each frame. A shallow DOF is more forgiving to overall compressed image quality because the blurry background typically does not change much from one frame to the next. The compression algorithm can retain more detail in the in-focus region of the video while compressing the blurry background more since compression there will not be as noticeable. As a general rule of thumb, around 10% of bandwidth can be saved by using a low DOF, but this is dependent on the busyness of the background and the exact DOF.¹

Aspheric Lens Elements Make this Possible

The cinema lenses used for shallow DOF cinematography must be able to deliver high image quality at a low f/#, or a steep focusing angle. The steeper the angle of light focused by the lens, the more spherical aberration, or variation of the focus distance across the lens’ aperture, there will be. Shallow DOF cinema lenses’ foremost design obstacle is combatting spherical aberration. High-end aspheric lens elements are incorporated into the larger cinema lens assembly to combat this (Figure 2).

Figure 2: Spherical aberration in a conventional spherical lens element (left) vs. an aspheric lens (right).

Aspheric lenses minimize the impact of aberrations through a more complex surface shape. Manufacturing aspheres is more intricate and difficult than manufacturing spherical lenses, increasing the price of cinema lenses utilizing aspheres for a shallow DOF. It may seem counterintuitive, but more expensive lenses are required to capture video that takes up less data. We can all thank the high-end aspheres inside modern cinema lenses for allowing us to watch entire seasons of our favorite shows on Netflix over a single weekend.

Aspheric Lenses at Edmund Optics^®

Edmund Optics^®’ high volume asphere manufacturing cell operates 24 hours a day to create thousands of precision aspheric lenses per month using state-of-the-art production and metrology equipment. Whether you need in-stock aspheres available immediately or fully-custom aspheres designed by our expert engineers, our skilled optical design and manufacturing engineers will develop a solution tailored to your needs. Contact our engineers today for application guidance or to receive an expedited quote.