By helmsm | Thu, 09/30/2021 - 21:10

Focus on Lenses for Broadcast TV

Published 10/1/2021

When it comes to producing uncompromised video for live television shows and streams, broadcast quality results depend as heavily on the caliber of both the lenses and the cameras themselves. It may surprise you to know that some high-end 4K/UHD lenses, such as big box sports lenses, can cost many times more than the camera itself.

In our previous blog, we discussed the importance of using industry standard B4 lenses without adapters to ensure the highest quality and proper alignment of the lens. This time, well be taking a closer look at the types of lenses typically being used in broadcast television today, including studio, news, and sports scenarios.

Ranging from HDTV to 4K/UHD resolution, the broadcast television marketplace features a wide range of lenses. Zoom lenses have variable focal lengths, such as 18mm to 135mm. A zoom lens that maintains focus as the focal length is changed (zoom range) is known as a parfocal lens. Expressed in millimeters, the focal length determines how wide or tight the shot composition will be.

Due to their flexibility, zoom lenses are very popular for broadcast production, especially for quick reframing of shots in run-and-gun ENG newsgathering and live sports coverage. A 10mm to 100mm range is said to be a 10:1 zoom, or 10 times the minimum focal length. Putting an optional 2X extender on a zoom lens--which doubles the focal lengthis often cheaper than buying a second, longer telephoto lens just for occasional use.

Besides the focal length, another key characteristic is the lens aperture. Ideally, buyers want fast lenses, with an aperture like f/1.4, which let more light hit the camera sensor, thereby performing better in low or challenging light conditions.

For live sports, big box lenses dominate because they allow fixed field cameras high in the stands to capture close-ups of game action from a considerable distance away. Now in resolutions as high as 8K, these massive lenses rely heavily on motorized control of zoom, focus, and aperture from remote control handles. Large zoom lenses often have built-in image stabilization to keep the picture steady.

Broadcast cameras must adapt to all types of environmental conditions when shooting high-value live productions, and lenses make all the difference. To capture accurate, impressive imagery, HD/UHD camera systems for broadcast studio and field production require lenses that can meet high standards, such as:

  • Capturing uncompromised imagery
  • Minimizing chromatic aberrations
  • Eliminating geometric distortion
  • Maximizing contrast performance
  • Avoiding vignette that causes lowered light distribution at the picture edges
  • Maintaining focus as the focal lengths on the zoom lens are changed

With their precision glass elements, broadcast lenses are attaining ever-higher resolutions, while striving for lower price points and smaller form factors. Nevertheless, broadcast and production professionals are extremely savvy and discriminating buyers, and producing live TV shows and streams are among the most demanding applications for lenses. Count on complete HDTV and UHD camera systems from Hitachi Kokusai to enable the utmost in uncompromised image capture for all your production needs.