Say what you like about film there's one incontrovertible fact, it's a visual medium. From the sumptuous vistas of The African Queen to the jaw-dropping bullet ballet of The Matrix, film is a feast for the eyes. And yet despite this it's actually possible to 'watch' and enjoy a film without being able to see any of it. The secret lies in two letters, two letters you may have seen in your local cinema listings, AD.

Audio Description isn't exactly new, but you'd be forgiven for never having heard of it before. In fact it's been around for years, it's only recently, however, that we've seen it start to take its place alongside subtitles and closed captions as a standard inclusion on film and DVD releases.

AD is a simple enough device to explain; basically put it's an additional audio track on which someone describes the action on screen during natural gaps in the dialogue, effectively creating a narration. In the years before it was widely available it was unlikely that you'd ever see a blind or visually impaired person at the cinema, at least not without a companion who's duty it would be to relate the action on screen as best as possible.

Personally some of my formative cinematic memories are of regular trips to the cinema with my mum, during which you'd find me frantically trying to keep up with the action on screen. Some films were particularly challenging, Dr. No for example, try describing Ursula Andress in that bikini to your mum!

Thankfully those days are numbered now as, more and more often, we're seeing films securing an AD track to accompany their big-screen release. Usually available on request at the majority of large cinema chains and multiplexes, it's delivered through a pair of wireless headphones synced with the action on screen, it's an unobtrusive and effective way of providing the service. On average most cinemas will run one new release a week with an AD track. What this means is that a huge cross section of society (Two million in the UK alone) are now able to enjoy something that the rest of us take for granted.

As well as limited big screen releases we're also seeing more and more DVD's coming with an additional AD option, think of it like a director's commentary but with less reminiscing! Take a few DVD's out of your collection and cast your eyes over the back cover, chances are one or two of them will bear the legend "Language: Audio Descriptive".

It's a huge step forward, but we're not there yet, hopefully at some time in the not too distant future you'll be able to go into any cinema and watch any film, any time, whatever your disability. In the meantime, next time you're watching a film, close your eyes for five minutes and see if you can tell what's going on, now turn on the AD track and you'll know exactly what I mean.

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