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How the LG G3 laser AF camera focus works

The LG G3 is the first phone we’ve seen to feature a laser focusing aid. You can easily see where the laser transmitter lives – it’s in the black bit to the left of the camera lens.

This kind of focusing system has been used intermittently for more than a decade in dedicated cameras, but how does it work?

Laser focusing is there to help out with a deficiency in the normal kind of focusing used by mobile phone cameras, and most cameras of all kinds – contrast detection. This focus system uses the normal output from the camera sensor, analysing it as the focusing engine moves back and forward in order to find out at which points the image is sharpest.

The issue? If there’s not much light, there won’t be enough contrast in the image to judge whether it is in focus or not.

The laser focusing aid provides this light. The output from a low-power laser is scattered out across the scene, giving multiple points of light upon which the contrast detection system can hang. Focusing on a little point of light on a subject is just as good as focusing on the subject itself.

Using this kind of focusing rules-out having to use the LED flash as a focus aid, which is particularly handy if you want to take pictures of people in poor lighting. The less time spent with lights flashing in your eyes, the better.

SEE ALSO: LG G3 vs G2: What’s different?

Taking photos of people brings up an obvious question – is this safe? We’ve all heard the stories about how firing laser pointers into people’s eyes is dangerous.

The LG G3 focus aid uses a low-power Class I laser, whose output is effectively split into fragments in order to give multiple points of focus. An already low-power laser’s output will be tiny by the time it actually reaches your subject.

This also means its range will be pretty low, but it’s with closer subjects that focusing in low light is more of an issue anyway.

But how does the G3’s focusing aid compare to the phase detection camera seen in the Galaxy S5? They’re actually completely different.

Phase detection is not a focusing aid but a completely different focusing system, although the Galaxy S5 uses it in addition to the normal contrast detect system.

In good lighting the Galaxy S5 will be able to focus more quickly than the LG G3, because the contrast detect of the LG will still use the ‘seeking’ movement that’s common to the focusing type. This is where the autofocus goes beyond the point of the subject being in focus, and then tracks back, in order to achieve the best focus.

However, you could argue that the laser aid of the LG G3 is a lot more useful in real life, as phase detection usually isn’t much use in low light. We’ll check out what the phone’s camera is capable of once we get an LG G3 in to review.

Next, read our Galaxy S5 vs LG G3 comparison

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