INSTAGRAM takes a perfect, crisp image from a smartphone and runs it through filters that crop it into a square and artificially wilt the photo to look as if it were taken with a 1970s snapshot camera. The process is entirely digital. A new app, called InstaCRT, goes a step further, marrying an app and truly analog technology.

Written by Swedish programmers, it takes an old-school approach. Take a picture or select an image from the photo library, and the program transmits the image via the internet to the developers' office in Stockholm. The image is loaded and projected on a one-inch square grayscale cathode-ray tube (CRT) display extracted from an old VHS camera. A digital SLR camera focused on the CRT snaps the picture, which is then uploaded to a secret URL passed back to the app. The image is stored in the photo library in its converted form. The photo might have scan lines or odd lighting. It is, after all, a real picture, and thus imperfect. (The developers note that they keep a copy of every picture taken for debugging purposes, but promise never to distribute any of them.)

It is a great play on the faux-faded look popularised by Instagram, which tries to evoke in the viewer a sense of distant nostalgia for something that just happened. By turning to a physical process, the developers successfully highlight the crazy artifice of the many snapshot apps, the appeal of which Babbage has never fully understood. Why age a perfect fresh photo except as a form of emotional manipulation?

With InstaCRT, though, Babbage too let himself be emotionally manipulated. For your correspondent, its pictures' graininess and a touch of "moiré" interference summons memories of late hours spent in basement terminal rooms in college, tapping away at white-on-black or green-on-black terminals, or watching fuzzy broadcast television on a tiny black-and-white set as a teenager.

LCD and other display technologies have largely replaced CRTs. LCD displays represent about 90% of television set sales in 2011, according to NPD DisplaySearch, which estimates almost no CRT TVs will ship by 2014. Just like the clicks made by a dial phone or the hisses and pops of LP vinyl, the imperfections of the CRT will fade from memory. InstaCRT might keep them alive for a while longer.