How can a film 73 years old be re-released in high definition?

The UK is now just weeks away from turning off the analogue TV signal for good, digital it seems is the way forward. Digital TV requires less broadcast transmission power, enables more channels to be broadcast in a narrower frequency band and most important of all it can transmit higher resolutions. I'm pretty sure the average consumer doesn't care about frequency bands or broadcast power, although they probably do care about the quality of the picture they can receive. The majority of the UK will be able to receive at least 3 Freeview HD channels by late October 2012; BBC HD, BBC One HD and Channel 4 HD. Fast forward five years and it's pretty likely that every free to air channel will be broadcast in HD. However, what I found curious was seeing as we're only getting a handful of HD channels in 2012, how can Gone with the Wind be available to buy on blu-ray considering it was first released in 1939?

It turns out the answer is actually pretty simple, 35mm film.

35mm film has the ability to record at resolutions far higher than what we refer to today as HD (1920x1080 pixels), basically all you need to do is use a film scanner to sample the analogue image to a digital image. It's actually very similar to a scanner you may have in your home, it reads dots per inch thus giving the resolution. The actual resolution of 35mm film is the subject of much debate although it's high enough to scan images at roughly 8000x4000 pixels (8k), 16 times the resolution of blu-ray. It's generally accepted that 4k (4000x2000) is enough to restore older films, evident by the fantastic quality of older films available for home viewing.

I look forward to a day when screens capable of 8k resolutions can be mass produced at a reasonable cost for the average consumer. Unfortunately we're probably in for at least a two decade wait.