Smartphones featuring dual cameras are becoming more common, and they will be integrated in more devices in future.
Mobile phone manufacturers provide dual cameras to help smartphone cameras work more like a professional digital single lens reflex (DSLR) cameras.
The main reason for the popularity in dual cameras is physical necessity. It is not possible to have a professional grade zoom lens in a smartphone as today's
phones are too tiny. Alternatively, creating camera zoom features in software quickly runs into limits of picture quality. But as lens
hardware decreasing in cost, adding another physical camera is now easy, with software switching between the two and interpolating images from both cameras.
With two slightly different types of sensors gives better dynamic range, the range of light and dark in scenes within which a camera can capture detail. Higher dynamic range and information about the scene give sharper details and richer colour.
Depending on real optical lenses rather than software to zoom reduces the digital noise that makes images grainy. Also, given less noisy images with more image data, it is possible to improve the quality of software zoom.
The second rear camera provides a much more vast number of possibilities. With two slightly different viewpoints means live images can be processed for depth
information per pixel captured, so that images get an extra dimension of depth data.
Since the distance between the two cameras is known, software can make triangulation calculations in real time to determine the distance to corresponding points in the two images.
The latest iPhone uses machine learning algorithms to scan objects within a scene, building up a real-time 3-D depth map of the terrain and objects. iPhone uses this to separate the background from the foreground to selectively focus on foreground objects. This effect of blurring out background details, known as bokeh, is a feature of DLSRs and not normally available on smaller cameras such as those in smartphones. The depth map allows the iPhone to simulate a variable aperture which provides the ability to display areas of the image out of focus.
More smartphones will have dual cameras for better picture quality and user experience.