[sdiy] [OT] CRT + Vidicon = analog convolution?

Gordonjcp gordonjcp at gjcp.net
Sat Jan 22 12:09:54 CET 2022

On Sat, Jan 22, 2022 at 08:11:07AM +0100, cheater cheater via Synth-diy wrote:
> The first time I heard of vidicons being used together with CRTs was
> when I read up on old TV stations and how they converted from 50 to 60
> Hz or between line amounts. They essentially filmed a TV, but the
> device eventually was an integrated CRT-Vidicon invention where the
> CRT and Vidicon both scanned horizontally. However, if you make them
> scan at 90 degrees of each other, you can use that for computation.

Go and look up what a "Scanimate" was, it'll blow your mind.  I think only one still exists in an operable condition.

All those visual effects you saw on 80s TV title sequences were done by applying modular analogue synthesis techniques not to the video signal itself (mostly) but to the scan voltages for a high-def CRT (800 lines or so!) with a TV camera aimed at it.  To make those wobbly side-to-side titles, they'd point the Scanimate camera at a title card (literally, a bit of white card with the titles drawn on) and apply a sine wave to offset the X scan voltage of the monitor, and so on.

Genius stuff, and nearly all gone now.  I'm amazed none of the video synthesis guys haven't built a reproduction given how cheap CCTV monitors and modular synths are.


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