Blog - Conservation

Posted - 14-02-2019

Conservation / Digitisation / ITV Cymru / Wales / Screen and Sound

Restoration, Restoration, Restoration

The HTV Wales archive is a significant record of Welsh popular culture, politics and history captured on both film and video and it constitutes a large part of the Screen and Sound Archive. An archive of that size and age will have an assortment of conservation challenges, especially in the area of restoration. By far the most common problem with old tape is Sticky-shed syndrome (SSS) or hydrolysis. SSS is symptomatic of the breakdown of the tapes’ polyester binder due to absorption of moisture.

The tell-tale squealing of the tape as it passes over the playhead and the accumulation of dirty deposits upon the guide and playhead indicate a tape has SSS. A tape with SSS will, amongst other issues, exhibit ‘crabbing’, i.e. the moving from side to side of the moving image, and if not treated continued playback could further damage the tape.

So how do we restore that believed lost episode of ‘Gwesty Gwirion’? The answer may surprise you! The standard practice is to bake the tape at low temperatures for relatively long periods of time, such as 130 °F to 140 °F (54 to 60 °C). Strictly speaking we don’t ’bake’ our tapes but instead use a commercial food dehydrator that removes all moisture from the tape pack. How long we do this to the tape will depend on the severity of the SSS; up to a week we’ve discovered is time enough. We have been successful with the majority of the tapes that have undergone the process, with many lost gems brought back from the brink of oblivion. You can see some of them on the ITV Wales YouTube channel or view them at the Library.


Martin Edwards

Posted - 14-09-2012



This post follows on from a conversation that began on twitter.

I was asked whether the Archive’s film collection had all been scanned at a 4K resolution (4096×30722 pixels, horizontal screen resolution). Unfortunately, the answer is no. The majority of our film collection that has been inspected and transferred to video, exists on digital tapes such as digibeta or dvcam at a standard definition. However, thanks to Cymal and the Assembly Government, we can now transfer the following formats; 35, 16, 9.5, S8 & R8mm up to the resolution of high definition 1080 if requested. In the long term, we hope to do away with recording to tape where the video will then exist as a file on a server for keep sake and for access purposes. Currently, we do send clips out to individuals and tv companies via an ftp connection but are constrained by the size of files therefore tapes will exist for that purpose for a while.

Most cinemas have converted to digital projection by now, where the standard is a 2K projection (2048 x 1080 pixels), which is double the resolution of high definition. Having said this, a good quality 35mm print is closer to a 4K projection. The multiplex in Carmarthen for example, projects all their films at 4K and I think that’s the way it’s going in terms of cinema projection and great for us resolution geeks as it’s closer to an actual film projection image.

Before we transfer any of our films, we fully inspect each reel for damage whilst observing for mould, oil, weakening cement joins to name but a few conditions. The reel can then be hand cleaned or to speed up the process, it can be put through our ultrasonic film cleaning machine. The reel is run through a bath of warm perklene solvent and then dried by following a path through the ultrasonic blowers. After this point, we’d scan it in real time to our mac’s hard-drive. If the film title were to be restored, it would be sent out to an external company in order for it to be scanned at a higher resolution via a 2K/4K scanner which would output DPX files. These would then be painstakingly be worked on by a team, frame by frame, by using a restoration programme such as DaVinci revival in order to clean up the image. For example, an old silent film running at 16 frames per second would have 16 frames to work on for every second, where there’d be 960 frames for a minute’s worth of footage. A sound film running at 24fps would consist of 1,440 frames for every minute. So, you can see how much work it takes in order to do a full restoration of an hour long title. On completion of the work and the grading, the digital intermediate can then be recorded back onto film, or as things are going, converted into a file such as jpeg2000. This is the format that arrives at the cinema where it then gets downloaded off a drive, ready for projection.

In 2010, the bfi re-released a restored version of The Great White Silence which is a good example of a 2K restoration where they’e also scored an experimental soundtrack to accompany the film that was originally silent. This title can be bought on standard definition DVD or on Blu-ray, which is a high definition DVD.
Film restorations are unfortunately expensive, where scanning at HD, 2K or 4K just increases the cost in terms of storage as the higher resoluion digital files are multiple times larger. Keeping the 35mm print/negative in a temperature controlled space will always make sense as the format is 100 years old and will almost undoubtedly outlast quite a few digital formats!




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A blog about the work and collections of the National Library of Wales.

Due to the more personal nature of blogs it is the Library's policy to publish postings in the original language only. An equal number of blog posts are published in both Welsh and English, but they are not the same postings. For a translation of the blog readers may wish to try facilities such as Google Translate.

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