Portrait mode, a major feature of the new Pixel 2 and Pixel 2 XL smartphones, allows anyone to take professional-looking shallow depth-of-field images. This feature helped both devices earn DxO's highest mobile camera ranking , and works with both the rear-facing and front-facing cameras, even though neither is dual-camera (normally required to obtain this effect). Today we discuss the machine learning and computational photography techniques behind this feature. HDR+ picture without (left) and with (right) portrait mode. Note how portrait mode’s synthetic shallow depth of field helps suppress the cluttered background and focus attention on the main subject. Click on these links in the caption to see full resolution versions. Photo by Matt Jones What is a shallow depth-of-field image? A single-lens reflex (SLR) camera with a big lens has a shallow depth of field , meaning that objects at one distance from the camera are sharp, while objects in front of or behind that "...