CNN's 2008 election night hologram was 35 cameras and chroma key

What you see

On the night of the 2008 US presidential election, CNN anchor Wolf Blitzer told viewers to watch what the network was about to do, then appeared to greet correspondent Jessica Yellin as she stood, faintly glowing and translucent, a few feet in front of him inside CNN's New York studio. Home viewers saw a composited broadcast image; CNN's own report, published the same week, states Yellin was in fact more than 700 miles away, at Barack Obama's rally in Chicago, and that Blitzer could only see Yellin on a TV monitor across the studio, not in front of him at all.

How it works

CNN's own technical account, published on CNN.com the day after the broadcast, describes the process: Yellin stood inside a bright-green circular room, filmed by 35 high-definition cameras spaced six inches apart around 220 degrees of the room, adapted from a system the article says was originally built by Israeli company SportVU for filming soccer replays. The feeds were composited in real time with the studio's own camera image, so the broadcast camera's movement matched the correct perspective from Chicago, a large-scale extension of ordinary chroma-key technology, in the quoted producer's words, taken to the Nth degree, not an optical hologram.

Viewing conditions and limits

CNN's own article is explicit: a hologram creates an image using coherent light, such as lasers, while CNN's technique used conventional cameras to capture multiple images from different angles. The company states producers deliberately added a blue glow around the composited figure so viewers would not mistake the image for something more solid than it was, and that the effect existed only in the broadcast signal; nobody physically present, including Blitzer, ever saw Yellin's image except on a monitor. CNN's own Political Ticker blog post republishing the story carried reader comments the same week objecting to the hologram label as misleading.

What it is not

By CNN's own distinction, this was not a hologram in the optical sense: no coherent light source, no interference recording, and no image occupying real three-dimensional space except inside the broadcast signal. It is more accurately a real-time, multi-camera virtual-set or chroma-key composite, a broadcast graphics technique scaled up with far more cameras than a single weather-forecast green screen. CNN itself put hologram in quotation marks in its own headline, a hedge acknowledging the label was marketing shorthand, not a precise technical claim.

• How closely does the described 35-camera SportVU-derived rig resemble later volumetric-capture studio systems, and did CNN or SportVU publish further technical detail?
• Was the same system used again by CNN in later broadcasts, and if not, what does that suggest about its production cost or complexity?
• Which specific broadcast graphics or compositing hardware combined the 35 camera feeds with the New York studio camera in real time?

CNN's own reporting explains, in the article that popularized the hologram name, exactly why the word does not technically apply, conventional cameras and chroma-key compositing, not coherent light, a reference point for any later broadcast reaching for the same label.