Like everyone else who writes about comics, or even has ever heard the word comic in their life, I am obliged by law to have an opinion on the upcoming film version of Watchmen.

(I’m not even going to consider the ‘motion comics’ thing that just came out. This is partly because I couldn’t access it even if I wanted to – the combination of not being available in the country where I live and not being available for the operating system I run stops that – but also because it was a bad idea back in the late 60s when they did it with Jack Kirby Captain America comics, and doing it to Watchmen is such a horrible idea that attacking it seems both too easy and rather cruel, like kicking a puppy that’s lost its legs).

But the film version is interesting, because it appears to be an illustration of a hypothesis I’ve had for a while now – that the quality of an adaptation is a function of the quality of the source material and the fidelity of the adaptation to it. The function in question being an inverse one. The worse the source material, and the less faithful the adaptation, the better the result.

That’s not exactly true, but it’s a surprisingly good approximation, and the reason why is fairly obvious.

Imagine you’re a film director, and you’ve been asked to adapt a book or comic or whatever for the cinema. We’ll give you the benefit of the doubt, as well, and assume that you actually intend to make a good film – that your motivations are primarily artistic, rather than the real motive of most makers of ‘comic book movies’ (wanting to be able to build a house entirely out of hundred dollar bills). We’ll also forget that you’re working in an industry that has an almost magical ability to carefully fillet out every trace of an idea from a film – the kind of industry where it was considered a good idea to make V For Vendetta but leave out the stuff about anarchy. How would you approach it?

There are roughly two approaches you can take. Let’s call them the babelfish and the Christopher Nolan.

The babelfish approach is – you take what’s on the page, and you put it on the screen. If you have to make cuts to fit it into three hours, cut the boring bits, but basically just put the source material on the screen. From the interviews I’ve read, from the photos I’ve seen, that’s what Zak Snyder trying to do with Watchmen. The director acts like a translating machine.

Christopher Nolan, on the other hand, is an extremely intelligent filmmaker, and he understands that the process of adaptation is one that must change the source material in fundamental ways. A film is not a novel or a comic, and The Prestige is not the same as the novel it’s based on, and Batman Begins has only a passing resemblance to Batman Year One (I’ve not seen The Dark Knight yet, but I imagine this applies there, too.

An intelligent adapter – whether Nolan, or Milos Forman adapting One Flew Over The Cuckoo’s Nest or Amadeus, or whoever – will essentially ask “How do I create the same effect as the source material, given the different strengths and weaknesses of the medium?” (or, if the source material is terrible, “How do I create the effect that the creator of the source material intended?”)

The approach taken by most of them seems to be to find what one might call the core of the material – the reason it works as it does. In the case of The Prestige this might be the relationship between the two magicians, in the case of Batman it’s a bloke dressing up in a bat costume and punching people.

You’d probably go into more detail than that, but you’d be looking at something like “Batman is a billionaire who saw his parents murdered as a child, and as a result trained his mind and body to perfection and devoted all his considerable resources to fighting crime. He does this by dressing up as a bat and, with the aid of gadgets, fighting grotesque villains who are mostly in some way warped reflections of himself, in a city that’s part Chicago, part New York, and part Gothic nightmare.”

You then look through the source material for those elements – and only those elements – that reinforce that core in some way. You then construct a new story around those elements. New characters can be created, old ones repurposed or merged, all in the service of that core. This way you end up with a film that is true to the spirit ( not The Spirit – a whole other rant) of the original.

It would in fact have been more than possible to do this with V For Vendetta– The core there is simple – “there’s a gun to your head, and you have to choose absolute anarchy or fascism. Which do you choose?” The fact that the film-makers ignored that core doesn’t mean it couldn’t have been done.

But this technique can only take you so far. There’s an idea in mathematics called algorithmic complexity. The idea is that a string (a number, say, or a sentence) contains only as much information as the shortest possible computer program that could produce it as its output. For example the number 123123123123123123123123… contains only the information loop(print’123′). On the other hand the shortest computer program that could produce Finnegans Wake would consist of the entire text of the book – you couldn’t compress it at all and still recreate it.

By analogy we can talk about a conceptual complexity – what is the ‘core’ of Watchmen ? What is it ‘about’? Is it about its own formal innovations (I could make a good case that the Giffen/DeMatteis Justice League is far closer to Watchmen than any of the grimungritty ‘serious’ stories of the same time)? Is it about power and responsibility? Is it about the limits of moral absolutism? The Cold War? What superheroes would ‘really’ be like? The way people’s lives are constantly affected by factors they don’t understand? The importance of love? The death of both the 50s ‘American Dream’ and the 60s counterculture and their replacement with Reaganism? The importance of the individual? How looking again at seemingly trivial childhood memories can reveal hidden depths? How even the most evil people can have moments of kindness, while the most decent are capable of horrors?

It’s about all those things and more. The only way you can sum up Watchmen is to actually hand someone the comic itself. In fact, arguably, you couldn’t do even that without handing them a bunch of other comics, a handful of newspapers from 1985 or 86, and a few decent books on mid-20th century history, to provide context… what Watchmen is about, fundamentally, is itself. Remove any of the elements – the page layouts, the pirate story, the essay about owls, the background story about Hooded Justice – and you have something significantly lesser than Watchmen, in a way very different from removing the framing story from The Prestige, which turned a mediocre book into an excellent film.

In particular, what Watchmen isn’t about is its plot, in a linear this-happens-then-this-happens-then-the-surprise-twist manner. The ‘A’ plot in fact is one of the weaker elements – taken out of the context of the rest of the comic it’s just another rip-roaring superhero yarn. Snyder’s film looks like it will bear the same resemblance to the comic as a transcription of the lyrics to Tutti Frutti would have to Little Richard’s primal yelling – it’ll be entirely accurate (apart from those terrible costumes) but nobody looking at it will have a clue what the fuss was all about.

I don’t consider Watchmen an Untouchable Classic – it’s not even Moore’s best work, let alone the Greatest Comic Ever as many would claim. But it’s unfilmable in a way many other works – even better works – simply aren’t, because it is so specifically itself. You might as well try to stage the Mona Lisa as a play, or novelise Beethoven’s Ninth Symphony.