Depth of Field and Mobile Devices

 Modern mobile phones have multiple camera lenses, each of different focal length and fixed aperture, each is, effectively, a separate camera.   The size constraints in a mobile phone design mean that the sensor size is small and the sensor to lens distance is also very small.  These factors produce a high Depth of Field even though the fixed aperture lens is very small.  So, in most cases, the whole of an image is acceptably sharp from front to back; it is not possible to set an even smaller aperture in order to create shallow depth of field images before capture.

On the iPhone and Samsung Galaxy the shallow depth of field effect is created after taking an image by blurring the background after the image has been taken.

The iPhone camera has a "Portrait" setting which allows the user to set the apparent depth of field and adjust the portrait lighting in post production.  Selecting the F symbol (in circle top left) the user exposes a pseudo lens aperture scale at the bottom of the image. 

In this example the camera has captured a sharp image from front to back.	If the pseudo aperture is adjusted to f1.4, the camera blurs the background of the image to create the same effect as decreasing the aperture size (increasing fNo).

The dogs head on the second image is sharp and the background is blurred.  The iPhone is good at recognising human and animal faces and so does a good job of guessing what the main subject was.

In the same way, other post production effects are possible including setting studio lights.  The following image is the same as the previous 2 images with different lighting settings and a different crop: