In the early days of TV, it was routine to tape over the recording medium after the initial air-date, which means that no video record exists of many of the pioneering moments in television.
One way that these early "lost" shows have been recovered is through transfers from old film stock -- the BBC used to distribute its shows by pointing film cameras at TVs and then sending film prints around the world to licensees. But film stock is incredibly volatile, and the old stock that is recovered is often "diseased" -- rotting into slime, too stuck together to unspool.
BBC R&D has published the first two parts of a three part series on the restoration of the only known copy of the first season of Morecambe and Wise on the BBC, discovered in Nigeria, where broadcaster RKTV had failed to comply with their licensing terms from the BBC, which had required them to destroy their prints after airing them.
These illegally retained prints were not in good shape, stored in a vault described as a "hot, poorly ventilated outbuilding in a small semi-rural settlement called Jos." The film was suffering from "tri-acetate film base degradation." It was so bad that the BFI wouldn't admit it into their vault, as it was emitting so much acidic vapour that it posed a danger to other film.
After spending a year in the home fridge of BBC Birminham producer Paul Vanezis (who refused to let his colleagues throw it a way), the film came to BBC R&D, who enlisted experts from Queen Mary University in London who specialised in X-ray Microtomography, a technique used to read water-damaged documents by producing 3D models of them.
But the film was not immediately amenable to traditional X-ray Microtomography techniques, as the large, tight rolls wouldn't fit in existing devices. So they tried an experiment, slicing the film into manageable chunks using laser-cutters, subjecting them to X-ray Microtomography, and then reassembling the slices with software.
There's still one more post to go, in which the researchers will reveal the outcomes -- but it seems likely something great will come of it (it would be weird to do a splashy, public-focused three part series about a failure).
If this kind of thing interests you, you should check out the amazing story of The Live Wire, a restored wire recording of the only surviving live performance of Woody Guthrie, which won a Grammy for technical accomplishment (and is an amazing album besides).
Although our tomography system may be cutting edge, this is one area where current technology could offer a substantial improvement. A femto-second (0.000000000000001 second) pulsed laser ablation system uses very short laser pulses such that almost no heat is generated in the cut object. We are still trying to track down such a facility for future work, but for now we continued to cut the film without serious incident. Each cut block was wrapped in cling-film, labelled and placed in a refrigerator awaiting its time to be scanned.
The film blocks were placed in the scanner and the voltage was set to 40 kV, a value which produced optimal contrast. Over 5000 X-ray images were taken as the block was rotated around 360 degrees, taking around 18 hours per scan to obtain the required image quality. Once complete, the 5000+ images from the blocks of film we had cut were reconstructed in 3D (a complex mathematical process) to compile ‘virtual’ chunks of the film reel. Flicking through the images, you might see part of Eric’s glasses, or a hand, but never a whole image because of the film curving and distortion.
To get our first glimpses of whole images, I wrote a fairly basic program that could manually warp a layer through the 3D volume to follow the contours of the film. The flattened images showed varying signs of degradation and in some cases laser damage, but considering they had been raised from the dead, they really weren’t bad. Until that point, I had had some doubts about the value of what we were trying to achieve, after all, we could never restore the film in all its glory, but only capture stills and maybe put together a short video clip. But as soon as Eric and Ernie’s faces and stereotypical poses began to appear, a huge grin spread across my face and I knew that this was a job worth doing. Much as I would have loved to continue dabbling with the film recovery software forever, this was not really my area of expertise; plus, this was only supposed to be a short departure from my dental research. At this point it was time to hand the task over to the boffins at BBC Research and Development to work their magic.