It's been just about impossible to artistically create a blurry foreground or background in a photo taken with a mobile phone or tablet camera because the small lenses don't display "depth of field."
"One of the biggest advantages of SLR cameras over camera phones is the ability to achieve shallow depth of field and bokeh effects," wrote Carlos Hernandez, a Google software engineer, in an April 16 post on the Google Research Blog. "Shallow depth of field makes the object of interest 'pop' by bringing the foreground into focus and de-emphasizing the background. Achieving this optical effect has traditionally required a big lens and aperture, and therefore hasn't been possible using the camera on your mobile phone or tablet."
With Lens Blur, which is a new mode in the Google Camera app, users can take a photo with a shallow depth of field using an Android phone or tablet and then change the point or level of focus after the photo is taken, wrote Hernandez. "You can choose to make any object come into focus simply by tapping on it in the image. By changing the depth-of-field slider, you can simulate different aperture sizes, to achieve bokeh effects, ranging from subtle to surreal (e.g., tilt-shift). The new image is rendered instantly, allowing you to see your changes in real time."
Lens Blur achieves the effect using algorithms that simulate a larger lens and aperture, he wrote. "Instead of capturing a single photo, you move the camera in an upward sweep to capture a whole series of frames. From these photos, Lens Blur uses computer vision algorithms to create a 3D model of the world, estimating the depth (distance) to every point in the scene."
After processing the information, the app re-renders the photo, "blurring pixels by differing amounts, depending on the pixel's depth, aperture and location relative to the focal plane," he wrote. "The algorithms used to create the 3D photo run entirely on the mobile device, and are closely related to the computer vision algorithms used in 3D mapping features like Google Maps Photo Tours and Google Earth."
Google Camera works on phones and tablets running Android 4.4+ KitKat.
Google often creates new effects and features for digital photographers. In December 2013, Google added the ability for users to include some flashy and decorative twinkles and snow to their online holiday photographs.