Test patterns are a delightfully arcane thing, originally created to solve an extinct problem – analog video signal fidelity.
In the primordial days of television, a set was adjusted through an elaborate set of small knobs – brightness, contrast, vertical hold, etc. Patterns evolved from the standard circles and lines (encapsulated in RCA’s Indian-head test pattern, above) through intermediate color versions (like the one I use for an avatar) to the SMPTE color bars:
If you’re too young to remember the circles-and-lines era of test patterns, you probably didn’t have a TV that had individual picture controls (though these settings have been somewhat restored in the menus of digital sets). At TV technology matured, the picture became less likely to drift out of alignment over time, and sets didn’t always come with controls.
By the time everything switched to digital, the test pattern had become almost ornamental to the home user. However, they’re still of use within the television industry and in other applications. When I was a print shop tech, for instance, we used cards to calibrate our color photocopiers.
Test patterns are by no means an exclusively American thing. UK readers will remember the BBC’s Test Card F:
Canadian viewers of a certain age may remember this:
(I grew up near the Canadian border and remember them using a slightly modified version of the SMPTE bars that had the CBC logo in one corner.)
And this fascinatingly baroque card is what you might have seen in Romania:
The test pattern enthusiast of today is encouraged to check out the Fantasy Test Cards YouTube page. There, you’ll find an impressive array of homemade cards, set to soothing stock music. I have a friend who swears by the channel as stress relief. And the videos are available in 4K, in case your set needs calibrating.