Sunday, October 30, 2005

Odd moments in tech history -- the analog laserdisc

Emily and I were reminescing today, as pre-elders tend to do, about payphones, record players, and other all-but-lost things. (Our daughter tells us that her pre-school has a "big-CD player", which we believe is a record player.) All of a sudden, perhaps for the first time in 20 years, I remembered the Laserdisc.

Talk about oddities in tech history. This was an analog media read by a laser beam; basically a record player in which the stylus was light itself. It was primarily used to distribute movies in the late 70s and early 80s. Wikipedia claims there are still a few million players in use, but even the hardcore fans admit the era has passed.

I remember a talk given by a very bright researcher at the National Library of Medicine. They were engaged in a large imaging project, and were storing the images on Laserdisc. I wish I could recall the numbers, but at the time there was a huge advantage over any available digital store. A comparable library, the Bristol Biomedical Library Archive, held 20,000 hi-resolution images. I think each image had an information density comparable to a 35mm slide. In my limited experience capturing the full information content of a 35mm slide can generate a 40MB TIFF. So the Videodisc held the analog equivalent of 800 GB of digital data, or almost a Terabyte of digital data. Even today a TB is a lot of data; that's almost as much as all my home drives combined. Analog storage has its advantages.

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