In the days when cameras had doors and Kodak had a business, the number 24 meant something. And until you got those two dozen precious shots back from the developer, you didn't know if you'd snapped duds or diamonds.
In the latest attempt to recreate this lost age of photography, the people behind the popular Hipstamatic iPhone app, which shoots low-fi photos of the sort Kodak's hit Instamatic cameras produced, has launched Hipstamtic Disposable.
The free app takes the same square images with digital "filters" that give shots a grainy, retro feel popular with hipsters (but a bit pointless if you don't have fantasies about living in the 1960s). The difference? You can't see your pics until you've taken 24.
To find out if this trigger-happy iPhone-owner could gain a sharper sense of the value of photos, I stroll to Hyde Park after lunch with a stripy-jumpered colleague. I shoot workmen, the office, the sad remains of snowmen, and Kensington Palace.
The app also allows your facebook friends to "share" the film. You all shoot away during, say, a night out. When you hit 24, the reel is "developed" on Facebook. The results? Well, judge for yourself from my shots above.