Although professional SLR cameras continue to look over the shoulder at smartphones, there is no doubt the enormous progress that this industry has made in recent years in the section of photography. Not only has it been a job of increasing sensors and capacities, since a miniaturization work has also come into play so that everything can enter without the size, thickness or weight of the mobiles, being excessively sacrificed.
And within this work, the sensors of the camera of the mobiles enter, able to obtain results that begin to rival those professional images that until recently seemed to be in an unattainable peak. Part of the success or failure of our mobile offering a good result has to do with the work that the sensors can do and of course with their ability to focus.
Approach methods
To do this, the lenses of our phones have automated electronic mechanisms to help focus, which prevents the user from having to make an adjustment manually, to try to save time achieving the expected result. These systems allow you to adjust the focal length of the lens to achieve a clear image in various lighting conditions. By moving the focus point of the lens, we can obtain the desired photo or at least the right clarity on a particular object or part of the image.
These electronic focus assist systems determine when an image is blurred to move the focus lens and reassess the situation. This analysis is performed by contrasting the elements of the scene such as borders, lines or textures. Depending on the mobile, we can have one or more systems to assist the approach, but the most common are:
PDAF (Phase Detection AutoFocus)
It is a very common autofocus system in today’s smartphones. It is based on image processing rather than mechanical adjustments, to obtain the correct approach. To do this, divide the image in two and then, the system works internally to move the image and align the lens accordingly. When it is aligned we get a focused image.
This system is very fast as it does not involve mechanical elements in the approach and is positive for focusing on moving images and videos. However, a percentage of the pixels will be assigned to the focus, although some terminals now replace this lack with Dual Pixel technology.
CDAF (Contrast Detection AutoFocus)
It is one of the most popular methods, but it has disadvantages with respect to the PDAF autofocus. This system is based on the contrast of the image that is received. The sensor moves the lens forward or backward to obtain the contrast of the image in the new position. Then results are compared and the best possible position of the lens is sought. It is a good system for static images but lacking in movement.
Auto-Focus Laser
This system uses a small laser transmitter and a receiver. To focus automatically sends a laser beam to the destination to be photographed and bounces to reach the receiver. Use mathematical algorithms to calculate the time it takes for lightning to strike and return. It is the fastest autofocus and works in very low light and is ideal for facial detection methods or selfies. On the contrary, it has long-distance deficiencies since the laser transmitter is not very powerful.