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How does the auto focus in the iPhone work? Is there a something mechanical in there to adjust the lens or is it completely software?

Google provides this article which suggests some camera phones do have mechanical focus mechanisms. I couldn't find anything specific to the iPhone however.

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up vote 5 down vote accepted

Autofocus on the iPhone is done via an electrical motor, moving the front lens backward and forward, and software that captures and analyses the image for best sharpness, which usually is the "sweet" spot. Recent versions of iOS probably offload the analysis to the image signal processor available since the Apple A5 chip.

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I may be wrong, but focus always require a combination of moving lenses + software.

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Theoretically, it's always been possible to refocus arbitrary images mathematically and with several shipping products like lytro.com this is now a reality with new sensor technology. You are certainly correct with 99.99% of sensors, focus implies movement of a lens. –  bmike Jan 7 at 20:09
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There are materials that change their index of refraction or shape with an electrical bias. A lens focal length could be controlled this way too. I would be surprised if an electric motor is involved, though I could imagine a MEMs device or a piezo-electric mounting material pushing the lens against a spring. This is all speculative.

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