How Smartphone Cameras Work – Laser Focus vs Contrast Detection

Cameras on smartphones have improved dramatically compared to a decade ago. That tiny little lens on your handphone may be miniscule, but it probably packs on some heavy firepower. A phone’s camera has become one of the key elements in judging the quality of a smartphone. Most of you think that when it comes to cameras, megapixels are all that matter, but whether your phone is 8MP or 16MP, it honestly doesn’t mean too much if your camera has horrible autofocus. Have you ever wondered how these little smartphone cameras focus so quickly onto your target object? Here’s a brief explanation.


The Traditional Contrast Detection

This type of autofocus is found in most smartphone cameras. The better lighting is, the better it will work.


How it works

The camera looks at the area you are shooting from nearest to the furthest points and analyzes pixels. The processor compares these pixels to find the the maximum difference in contrast ( the “whiteness” and “blackness” of the area). Scanning the scene with contrast detection will help the camera guess what to focus on.

Have you seen your screen go from blurry to clear, to blurry, and back again to perfect focus?

By going from nearest to furthest, the camera actually goes beyond the point of optimum focus, returns back to focus.

How quickly contrast detection can work really depends on the light conditions and the microprocessor of your smartphone. If the scene is bright,then the point of contrast is easier to “see”; if the microprocessor is powerful, the camera figures out the point of contrast much more quickly. Of course, if your object is moving, contrast detection will work poorly.

The Cutting Edge Laser Focus Technology

Newer smartphones are now beginning to utilise Laser Focus technology. They are better for taking photos on the go and pretty much for those with shaky hands. They do fare well in low light conditions as well. An example of such a smartphone would be the ZenFone Selfie.


How It Works

The camera is shoots out an infrared laser which will hit the object , bounce and come back, regardless of how dark it is. Lighting conditions seldom matter here. Hence Laser Autofocus is the best of shooting technology for low-light photos.

However, lasers on these cameras are pretty weak. They aren’t your lightsaber quality lasers you are going to see in The Force Awakens. It’s a camera, not a beam rifle. Therefore, it works only when the subject is close enough for the laser to bounce back. So if you are going to take a shot in the Alps, laser focus is pretty much useless. The saving grace is that all laser autofocus smartphones currently use both laser focus and contrast detection; so when the laser focus isn’t suitable, the camera can tap on contrast detection.

Phase Detection Technology

Who uses this tech? Loggerheads Apple and Samsung. You can find them in the iPhone 6 and Samsung S5 and above,


How It Works

Apple and Samsung have chosen this as their arsenal of choice because it is capable of continuously refocussing a scene when a subject is moving. Interestingly, the lens of a camera is curved. When the camera captures a scene, the image on the rightmost part of this curve is compared with the image on the leftmost part of this curve. These 2 images are slightly blur but the camera can calculate the difference of clarity between these two images. In so doing, it figures out where the best focal point.

This type of autofocus best works with a moving target of course, but it doesn’t fare too well in poor lighting conditions and when both your subject and background changes simultaneously.


All these technology have their own pros and cons. However, laser focus and phase detection technology seems to be the more modern and popular choice these days. So before you go around telling people how great your camera is due to its huge megapixels, think about the autofocus first.

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