Announced earlier this week, Nokia's Camera Extras app is now available from the Windows Phone Marketplace for the Lumia 610, 710, 800, and 900 in the US and China (other markets can expect to get it in July). Though it masquerades as an app download, the app itself doesn't really do anything — opening it just tells you to press and hold your camera button to access your camera app as you normally would, and that's because Camera Extras actually adds four additional features in there: a self timer, an "Action Shot" mode that lets you take bursts of photos to capture an action sequence similar to features introduced on recent HTC and Samsung models, panorama capture, and "Smart Group Shot." Of the four, Smart Group Shot is the most interesting — it uses technology from Scalado to take several shots of a group of people and assemble the "best" heads into a single composite picture, so that if you're unable to get a picture where everyone is smiling and has their eyes open, you can assemble the best heads onto the best bodies.

In our brief testing on a Lumia 900, we found that Action Shot was unable to produce bursts fast enough to get the job done, but it's a feature that we'd expect to play a prominent role in future Lumias (with PureView technology, hopefully). If you'd like to try it for yourself and you're in the US or China, you should be able to find it in the Marketplace now.