The Apple iPhone 4S has quickly become one of the most used camera phones on Flickr, with data from the photo sharing service showing that the device is now the second most used mobile phone on the site

The news is perhaps not so surprising when considering the device’s focus on photography — which saw the camera upgraded to 8 megapixels — and its popularity with consumers. Apple is estimated to have sold more than 4 million units over the first weekend after it launched in America, and it has sold out in a number of other markets across the world.

Although Flickr’s Camera Find page does not show dates or exact usage statistics, the data shows a rapid rise in the posting of images taken on the iPhone 4S right from when it was first launched in the US and selected markets in October.

Screenshot 5 The iPhone 4S is now Flickrs second most popular camera phoneThe iPhone 4S still has some way to go to overtake its predecessor, the iPhone 4, as the most used camera on the site, although usage of the latter is already beginning to show signs of peaking.

Apple dominates the list of most used smartphones, with the iPhone 4, iPhone 3GS, iPhone 3G and now the iPhone 4S all amongst the top five, a line-up that is completed by the fifth placed HTC EVO.

It is perhaps even more impressive that the iPhone 4 has been the most used of any device –including standalone cameras — since June 2011,when it overtook the Nikon D90, as CNET reported.

Screenshot 6 520x151 The iPhone 4S is now Flickrs second most popular camera phone

While the popularity of the iPhone 4 and iPhone 4S on Flickr is not indicative of all photos posted to the Internet, it is a major sign of the popularity of Apple’s devices for capturing photos. Considering that iOS 5 is already the seventh biggest photo client for Twitter — ahead of many dedicated Twitter photo sharing apps and sites — Apple’s decision to invest in improving the camera on the iPhone 4S appears to have been a wise one.

iPhone photographers may be interested to know that tap tap tap‘s recently relaunched Camera+ app, which now includes the ‘VolumeSnap’ feature which Apple had previously forced to remove from the app.