Microsoft has launched its first-ever iPhone application is a slick photo viewer with a browsing capability that handles a large number of photos on a mobile device screen.

The Seadragon mobile application is free through Apple's application store. It a product of Microsoft's Live Labs division, which focuses on developing web-based technology and applications.

Seadragon incorporates the Deep Zoom feature, which is also integrated into Silverlight 2, Microsoft's multimedia tool. It allows a user to quickly magnify a particular area of a photo, regardless of its size.

Microsoft said the aim of the mobile application is to let users view even wall-sized displays on a mobile device, regardless of the amount of bandwidth on the network.

Seadragon renders documents as little thumbnails, and a double-tap brings it into focus. A reverse pinch on the iPhone's touch screen kicks in the Deep Zoom, revealing sharp detail.

For the iPhone, Seadragon comes preloaded with bookmarks that deliver content from organizations such as the US Geological Survey for photos and the US Library of Congress for documents.

But the viewer could also be used to browse email or other content. "If you can think of a data type, this can be applied to it," said Microsoft developer Ben Vanik, in a short video.

Seadragon mobile can be used in conjunction with Microsoft's Photosynth application, which takes batches of digital photos and stitches them together. In order to create a Deep Zoom image, Microsoft offers a tool that will prepare the photo or document.

Of the 16 comments about Seadragon on Apple's application store, nearly all were positive. One user called it "brilliant" especially since Microsoft was treading on "alien territories" by writing an application for its competitor's platform.

Microsoft didn't say when Seadragon would be available on other mobile devices or operating systems, including its own Windows Mobile.