We live in a digital age. Film, tape and vinyl, which we had for most of the 20th century, gave way to digital cameras, DVDs and MP3s. Very recently Kodak, the largest maker of photographic film, went bankrupt. London is switching off its analog TV signal is year. 4G mobile signals are going to drown out the analog TV signal in other parts of the country, until they eventually shut it down completely in these areas too. Cinemas have started to move towards digital projection.
One of the few analog technologies still going strong is radio. No matter how hard the UK government tried to move people away from FM and into digital radios, DAB digital hasn’t caught on enough to justify switching off the FM signal just yet. Shortwave radio is also alive and well because its signal is capable of bouncing off the ionosphere, which means it can travel ridiculously long distances.
But, radio aside, it is the end of an era.
At the same time, most people assume that digital is an enhancement over analog, some sort of modern upgrade on previous, antiquated technologies. This is not always true. Let’s talk about three of these in particular: TV, audio and photography.
An old-fashioned analog signal gets progressively worse as you get away from the broadcast antenna. If you get very far from it, you may still be able to watch your favourite programme. Perhaps in black and white, with a lot of “snow” and a bit of white noise in the background, but it will be watchable. With digital it doesn’t work like that. If you are close enough to the antenna you get a perfect signal—exactly the same perfect signal everyone else gets in your area. But going farther from the antenna, there will be one very specific point in which the signal will almost immediately screw up and you won’t be able to watch your programme at all. This is called the “digital cliff”.
And here is the cliff in action. This in analog TV would be perfectly watchable, but because of the bad weather the signal keeps dropping off the cliff and disappearing altogether:
To squeeze so many digital channels into one signal they need to compress the picture, losing part of it in the process, for example JPG images. This creates noticeable defects (also called “artifacts”). You may have noticed them, especially when there are rolling credits on the screen or when people wear stripy clothes, or when things are just plainly pixelated. You wouldn’t see these in analog. A good analog signal is way better than an compressed digital one.
It’s the same with music. Imagine sound as a waveform which is basically a smooth line going up and down. To convert this to ones and zeroes you need to “square it up”. Splitting it in the horizontal axis (time) is called sampling: a CD’s 44.1kHz means that you sample the sound 44,100 times per second. On the vertical axis (amplitude) it’s called quantisation: 16-bits means that this axis has 2 to the power of 16, i.e. 65,536 levels. So we have turned a curvy, smooth waveform into a jagged, boxy signal which looks like a staircase going up and down.
That’s how it’s stored in the CD, and when you then play it there are special algorithms which “smooth it out” again as much as possible. But it will never be exactly as it was before. In the case of MP3 compression, the loss of the original signal is many times worse. You won’t notice it with pop songs because they tend to be constant in their sounds, but you’ll probably notice it if you play something that includes silences.
A new, unscratched vinyl record is of better quality than a CD because it has kept all the infinitesimally small detail of the sound whereas the CD didn’t (although most people can’t tell the difference). The good thing with the CD is that it’s more robust and shouldn’t deteriorate much with use.
Analog film captures light in the “grain” (randomly distributed on the surface).
Digital camera sensors capture light in an orderly grid of picture elements (pixels):
As with audio, the colour levels you have in analog photography are infinite, whereas in digital photography they are around 16 million. But that’s not the problem, because 16 million colour shades are much more than the human eye can distinguish anyway. The main problem is the resolution. A good colour film with ISO 100 sensitivity has much better grain detail and colour depth than an average digital camera (ISO 100 is equivalent to around 22 megapixels). There are few digital cameras which can reach this resolution today, but we’re slowly getting there.
Another thing that digital cameras can’t do well is infrared. This is photography in a light spectrum beyond the visible range. It has fascinating properties such as detecting diseased plants and seeing through clothing. Infrared photos have an otherworldly, eerie beauty.
However, most digital camera manufacturers have decided to filter out most of the infrared light because it could confuse the autofocus calculations or soften the image. You can convert a digital camera to infrared by performing a very delicate operation to remove the IR filter (or pay someone a lot of money to do it for you) and it’s not an easily-reversible process.
As far as print longevity is concerned, a cheap but well-processed silver print (darkroom-produced) will last more than 500 years. The average digital photographic paper will last a few decades. The very best and most expensive archival-quality ones will last around 400 years. Not that this is a major concern, but still.
No-one in their right mind would advocate a return to analog, and neither do I. Digital is quicker, cheaper, more convenient and versatilite. But consumers must educate themselves as to its limitations. When you buy a top-of-the-range high-definition plasma TV and you end up watching your news in near-YouTube quality, digital has failed. When you go to the cinema to watch the latest blockbuster in incredible sharpness but with a flickering trail left by fast-moving objects, digital has failed. When you listen to a classical symphony in your expensive hi-fi and you hear hiss in the silent moments, digital has failed. Vote with your wallet and don’t settle with poor quality digital. Hopefully manufacturers will get the message.