Alley in Pisa, Italy

by Lars Kotthoff

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Likely this will be the same as the color depth in bits per channel.

For digital cameras it can be 8bit or 12bit and sometimes as high as 14bit. What is it for the IPhone 5?

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For all intents and purposes, that would be 8-bits per channel or 24-bit per pixels because what you get out from the camera is a JPEG image and that is its limit.

The sensor internally is highly likely to have a greater bit-depth, maybe 10 or 12 bits per channel. This is actually needed to produce an 8-bit-per-channel JPEG because sensor output is linear but JPEG levels follow a gamma curve. If you have an 8-bit linear sensor, you would not be able to fill out all possible values of a JPEG image.

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The discreet brightness (color) values of a JPEG image are not linearly spaced in brightness? I presume they are and the difference between the scales exists to make the image look correct as a photo. Also, can other apps not get the data more directly, or is this built in at a hardware or OS level to only provide an already constructed JPEG? –  alan2here Jan 14 '13 at 18:33
    
Sorry, just after a little more info then I'll mark as correct, it's a good answer. –  alan2here Jan 14 '13 at 18:39
    
They are not supposed to be linearly spaced in a JPEG. If someone were to produce a JPEG with linear values, it would look wrong. Apple does not give direct access to the hardware. That is probably to abstract the differences between cameras so that software that use it can work with future generations of iPhones. –  Itai Jan 14 '13 at 18:41
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No. No app gets more than 8 bits per channel. As I said, there is no information on the internal linear read out and Apple has good reasons not to expose that information. –  Itai Jan 14 '13 at 18:57
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I understand now. Thanks again, I couldn't find this information elsewhere, your super helpful. –  alan2here Jan 14 '13 at 19:13

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