What is the purpose of a dual LED flash?

Question

I see that some smartphones now have dual LED flash.

What exactly is the purpose of a dual LED flash? Anything to do with brightness? What can a dual do that a single flash cannot? Would a triple LED flash be a possibility even?

Answer

The distance from which you can light subjects with a flash is proportional to square root of luminous power due to the inverse square law. A dual LED flash can emit twice as much light as a single LED, which means you can lit subjects 1.4 times further away. It also draws twice as much power.

A triple LED flash would increase your reach 1.7 times compared to a single LED (1.2 times compared to dual LED). So the difference is not as significant as when stepping from single to dual, but increase of manufacturing costs and power drain is similar. Triple LED flash is not unheard of - Pentax Optio W90 uses three LEDs to aid during macro shots. As they are placed triangularly around the lens, they effectively create a ring light effect.

Generally, if you need more light than a dual flash, you'll be happier with a Xenon flash. A Xenon flash would also let you add regular speedlights off-camera in optical slave mode, but cannot act as a continuous video light / torch.

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