Make “3D” photos with a Nokia phone? When we first learned of Photo 3D and what it promises to do, we were skeptical. As longtime photographers, we happen to know that even pseudo-three-dimensional images are possible only by capturing two distinct images, each from a slightly separate vantage point, one to be viewed by the left eye, one by the right eye. Then, the brain can work with the images’ differences to synthesize a 3D view.

Indeed, this explains why we have two eyes and why, when you go see a 3D movie, you have to wear special glasses. Only by providing each eye with its own image can stereoscopic photography work.

So how is 3D possible on a smartphone, which has but one camera with one lens and one image sensor and one viewing screen, and no special glasses? In fact, Photo 3D, developed by an outfit called Digital Footmark and available from Ovi Store for $1.99 (USD), does not create the kind of 3D images you see at the movies. No, you won’t see objects thrusting towards you as if they were extending out from your phone’s screen.

The images here are more like what you’d see in a Viewmaster, a toy (invented more than 70 years ago!) that reveals pseudo-3D views of the Grand Canyon and Disneyland. The depth that Photo 3D adds to standard 2D photos seems to extend away from you, into the background. It’s all an illusion, but the process, we’re happy to tell you, works remarkably well, all things considered, and the app is great fun.

Unfortunately, dear reader, you won’t be able to experience this illusion of 3D right here, on this blog page, for reasons that will soon be apparent. But read on and we’ll explain how the Photo 3D process works and how the final images manage to reveal an illusion of depth. (If you are in a hurry, you can scroll down to see a video of the app in action that Digital Footmark has helpfully posted on that big video jukebox in the sky, YouTube.)

Here’s how Photo 3D does what it does: First, you choose one of the photos stored in your phone’s memory. Once it’s open in Photo 3D, you use your finger to build what the app calls a “depth map.” What this means is that you will select certain areas of the image to indicate to the program those that should appear further back from the flat surface, or plane, of the touchscreen and those that are closer.

Once this mapping is done, the app is them able to show these different sections of the image moving in relation to each other as you move your image to the left or right, or up and down.

This movement is accomplished either by “pulling” on the image with your fingertip or by tilting the device back and forth. Either way, if the mapping has been done correctly, you’ll see the foreground elements move further and more quickly than those in the background, thus creating the illusion of parallax. It’s parallax, of course, that provides the brain with clues about the relative distances of objects that one’s eyes are seeing.

Clearly, the accuracy of the depth map you create is crucial to creating a realistic illusion of 3D. To make this map, you simply draw on a photo with your fingertip, outlining selected objects and filling them in. There are three settings to adjust. One is “brush size,” or how large an area your fingertip affects as you draw with it. A smaller brush size is very helpful in tracing the edges of objects, especially when they are jagged. Wherever you miss following an edge accurately, there will be a flaw in the final 3D presentation; you may see an ear, for instance, fail to move with the rest of a person’s face. Accuracy in edges is especially important with objects in the foreground. The larger brush size is useful for quickly filling in larger areas. As you outline and fill in a section, you’ll see it become tinted. Like so:

The next setting is “brush depth.” This is used to indicate that some sections of an image are deeper, or further back from the image plane, than others. Sections marked as closer become tinted in green as you map them with your fingertip while those further back turn different shades of red.

Finally, there’s a switch that toggles between Flat and Landscape. This can do some automatic depth mapping, but it may not always interpret your photo properly. There is an Undo button, which removes your latest brush stroke – and only that last one, no more – but it doesn’t seem able to undo the full-image mapping executed by the Flat/Landscape switch. So, be careful. Photo 3D maintains its own gallery of processed photos, though, which means that should you make a mistake, you can always go back and try again.

Here’s that demo video we mentioned up top, showing this app in action on the Nokia N8:

Perhaps this app will motivate you to explore 3D photography in general. The field happens to enjoy an enthusiastic, worldwide following. And Photo 3D, it turns out, is not the only 3D-related app available in Ovi Store. An app called 3DPhotoFree, which we’ve not yet tried, seems to work on the same principle as Photo 3D; it’s available at no charge. And for those shooting “real” stereoscopic photos, involving a pair of distinct images, there’s Stereo Base Calculator, which helps in setting up the right camera angles. And finally, there’s 3D Photography Forum, another free app that keeps enthusiasts connected to a website by that very same name. Happy shooting!

Photo 3D is available in Ovi Store for $1.99 (USD).