It's not just the instant satisfaction that drives app popularity. Peter Lang, known as Furkidsinhk, co-organised HK InstaYay - a monthly meet-up for Hong Kong Instagram app users. 'Apps are free, or low cost, so people shoot more. They're easy to use; you don't need many photographic skills. Even my technophobic wife understood Instagram and Camera+ immediately. She's now hopelessly hooked,' he says.

All this ease and convenience, of course, is changing our relationship with photography. Fitzpatrick says that apps allow him to react to opportunities quickly, edit the work on the go and share it in minutes via social media. 'People used to spend hours in a darkroom to achieve certain effects,' he says. 'Now you can do it in seconds. The line between amateur and professional is blurring; digital technology is the reason.'

Lang adds: 'For many, photo-enhancing apps have sparked an interest in photography. They've made photography more popular. Prior to iPhoneography, even processing digital images was less common. Most people didn't have the skill or patience for post-production computer editing.'

Lang says one of the attractions of photo-sharing apps is their social aspect: 'Today you'd be hard pressed to find a city that doesn't have an Instameet. We've done photo-walks learning about the history and culture of the location.'

For many professionals, camera apps have also made their job easier. Low says that Viewfinder Pro, for example, is perfect for location scouting. 'You can check different focal lengths and lenses for most medium format camera brands. It'll show exactly what the photographer will capture.'

Whatever your photos need, it's likely there's an app for it. Camera+ includes light settings, scene modes, post-production filters, borders and cropping capabilities.

For a choice of lenses and filters with unpredictable colourisation effects, try Pudding Camera, which is particularly popular in Hong Kong.

For a vintage feel, Fitzpatrick favours Hipstamatic. But the app comes with only a limited range of lenses and film stock, and additional ones cost extra.

Advanced Photoshop Express from Adobe is an obvious post-production editing tool. When asked what the latest, best camera app is, Lang reels off a list of apps that provide '90 per cent of Photoshop, done in 10 per cent of the time'. Among these are Snapseed (tiff support, filters, social media sharing, specific editing); Filterstorm (saturation, text, colour balance, curves, vignetting, noise reduction - the list goes on); TouchRetouch (it is what it says it is); Dynamic Light (dynamic colour ranges and improved luminosity) and LensFlare - great for fans of J.J. Abrams films such as Star Trek (2009) and Super 8.

If you're tired of stitching together the perfect panorama, apps such as Pano guide - or shoot - while you point. But beware - Pano stitches up to only 16 images and compresses them to a low-resolution image. Photosynth, surprisingly developed by Microsoft, is limitless and has a guide with automatic and forced image capture. Navigating the scene is comparable to Google Maps' street view. Better still, upload your images to your online Photosynth account, download a small program to your computer and enjoy the 360-degree feel on a larger screen.

For humorous warping effects, try Fat Booth. If that doesn't make you laugh, MyCeleb will tell you your star lookalike, with often hilariously embarrassing match-ups. Pocket Monet turns your photos into an Impressionist painting.

Meanwhile, phone cameras are becoming more sophisticated, too. The iPhone 4G boasts that it has what 'might be the best camera ever on a phone'. It has 8-megapixel resolution, a larger aperture, better colour accuracy and facial recognition.

Will apps continue to develop with increasing ability and complexity? Lang sees a future boom in amateur photography. 'IPhone and apps will cause a marked decline in sales for compact cameras. Why spend time sitting in front of a computer working with Photoshop unless you're a professional?'

Fitzpatrick, however, reckons, 'Apps will fall out of fashion eventually. A few years from now, a lot of app-edited photos are going to look very 2011, and not in a good way. We'll return to more straightforward photography.'

But before that, there's one thing he'd like to see in an app. 'A clich? detector. One that stops you taking fake Polaroids of dogs, cats and restaurant meals. Or isolating red roses or autumn leaves against black and white backgrounds.'