The sight of Alexa Chung focusing her bright turquoise toy camera on the Chanel catwalk last year was proof, if any were needed, that the Diana+ is the camera du jour. Lightweight, colourful and cheaper than a handbag, with limited editions designed by the likes of Paul Smith or the White Stripes, they have an obvious appeal to the teenagers you see cooing over the range at Urban Outfitters or at the Lomography shop in trendy Spitalfields Market. But they are also cool enough for Hoxton hipsters intent on exploring the low-fi aesthetic of analogue photography.

Serious photographers tend to prefer the Holga: it's a bit bigger than the 35mm Diana+, but uses medium-format film, which is relatively hard to come by and expensive to process. Both have fixed lenses and only one shutter speed, but they can produce all sorts of startling effects.

Anything goes in the Lomo approach to film photography, the website Lomography.com assures us, even "boring, brou-ha, left toes, blurred nothings".

Hmmm. Some of us would rather not waste £1 a shot developing rubbish snaps, which is why we have come to Brighton for a half-day "Holga and Diana" workshop at Create Studios.

"Lomos are flaky cameras," says tutor James Kendall, cheerfully. "That's part of the appeal: they're like those friends who never show up at parties but when they do, the party's always a blast. When your Lomo pictures go right, you get incredible results."

And people all around the world are getting those great results: among the thousands of images posted on the Lomography.com gallery are many dazzling results, from gorgeously saturated colour to faded images straight from a 1950s magazine. There are optical distortions, weird lighting, blurry silhouettes, superhero skin tones, and ghostly overprinting.

Big-name "Lomo amigos" include actor Elijah Wood, musician Jack White and fantasy writer Neil Gaiman, attracted by a low-fi aesthetic and the possibilities of "happy accident".

First, a little history. The first Lomo camera, the LC-A, was a cheap 35mm compact with a rather good fixed lens. It was first made in Russia in the 1980s, and introduced to the west by some enterprising Austrian students a decade or so later. Lomography.com still sells LC-As (now mostly made in China) but they're not cheap; it also has a range of more affordable and even more low-fi alternatives.

The Holga, which we are using, is all plastic and, although relatively large, weighs next to nothing. The Diana+ is based on a toy camera from the 1960s. Then there is the funkiest-looking of all, La Sardina, made, as the name suggests, from recycled tin. All are are prone to light leaks, which, in Lomography, is a good thing.

Now for the theory. There are only two modes, James tells us – sunny and cloudy – so you shouldn't even think of trying to take pictures indoors without a flash. Outside, look for shadows – if you can't see any, go read a book or something.

He produces little cards for us to use to calculate distances for accurate focusing, and demonstrates how to balance your camera on a folding wooden measure at exactly the right distance for close-ups. I make a mental note to concentrate on the middle distance instead. Make sure you wind the camera on after you've taken your shot, he tells us. You may want to consider throwing away the lens cap, too – so you won't forget to take it off.

Forewarned, we head out into Brighton. It's a drizzly Saturday – not much in the way of shadows – so there's a challenge to start with. But Create Studios is ideally placed for locations. The immediate vicinity is grungy urban: great graffiti, scruffy industrial buildings, lots of rubbish, odd patches of flowers. But it's only a few streets away from the warren of fiercely independent shops that is the Lanes. There's much to catch the eye here – mosaics in the pavement, windows full of hats, a knitted Brighton pavilion, transvestites in killer heels and men in tiger suits arguing at market stalls.

James, who edits Source, a local listings magazine, is a good guide, offering a running commentary on the sights along with tips for good pictures. "Go for old-fashioned shots," he suggests, to go with the old-fashioned technology. Crowds are easy, dogs even better. "Do shoot into the sun – you get good effects that way." Not an option that afternoon, sadly.

There is something hugely liberating about going out with a group of photographers. In the ordinary way, I'd never get down on my knees before a bunch of green plastic ducks. Or hold a piece of string to a girl's nose to make sure she is in shot (actually, I let James do that – I planned to capture the moment for posterity). In the gardens around the Pavilion, we poke our cameras into a bush to capture a man practising some yogic discipline in his shorts, and squat to focus as hen-partiers in top-to-toe union flags strike poses for us.

By the time we reach the beach, the rain has driven everyone away from the merry-go-rounds and damp deckchairs. Once we've used up our two free rolls of 120 film (a couple of dozen pics in all), it's time to go our separate ways. I buy some more film, in hope that the weather will improve. If my borrowed camera hadn't jammed as I was on my way back to the Grand, I just know I'd have got some brilliant night images of the pier and the streams of traffic below my hotel room balcony. For the next couple of weeks, I see great Lomo shots everywhere. I don't want to give the Holga back. Maybe I'll splash out on an LC-A. Then I get my prints back. Almost every bloody shot is overexposed, fuzzy, and with lots of unintentional camera shake. Even the ducks. (I know – James did warn us. Yes, I should have taken up the offer of his folding rule.) Maybe I won't bother with an LC-A. I'm told there are lots of smartphone apps that can give you the same effects …

• The course was provided by Create Studios in Brighton (01273 601965, welovecreate.com). Its next Holga and Diana course is on 28 October, £75pp. See Lomography.com for events and workshops in London, Manchester and overseas. Zoingimage in Sydney Street, Brighton (zoingimage.com) sells lo-fi cameras and film. Urban Outfitters (urbanoutfitters.co.uk) also sells Lomo cameras online and in store. Travel from London was provided by Southern (southernrailway.com, singles from £15.40), and accommodation by the Grand Hotel (0871 222 4684, devere-hotels.co.uk, doubles from £85). For inspiration, check out the LomoWall at the Museum of London (museumoflondon.org.uk), an exhibition of almost 30,000 lomo photographs from 32 countries, until 6 January 2013