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Old Dec 2, 2012, 04:24 PM   #1
DirtySocks85
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iPhone 5 focal length math

So I'm fairly new to photography, and I expect that my math could be a bit off, but I was trying to figure out the focal length (per sensor size) on the iPhone 5 and this is what I came up with.

So the listed focal length in the EXIF data on my iPhone photos is 4.13mm.

I believe I read somewhere that the crop factor of the iPhone sensor on the 4S and the 5 is 7.5 (if this info is wrong it throw off everything else).

So if I'm understanding how the focal length math works, this is essentially the same angle as about 30mm on a full frame sensor or 50mm on a 1.6 crop factor sensor (such as most entry level DSLRs).

Would this be correct? This is mostly just a thought exercise, but would be good information to keep in mind while shooting with my iPhone.
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Old Dec 3, 2012, 12:00 AM   #2
mulo
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the iPhone 5 has a 4.1mm focal length lens with a crop factor of 8.05 totalling a FF field of view of around 33mm, or a 1.6x crop field of view of 20mm
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Last edited by mulo; Dec 3, 2012 at 02:42 PM.
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Old Dec 3, 2012, 10:30 AM   #3
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Ah, thanks for clearing that up Mulo!
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Old Dec 3, 2012, 11:03 AM   #4
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Focal length is a property of a lens, and is unaffected by the sensor size. I say this not to be pedantic, but because it's important not to get these types of things confused. Focal length does not change with sensor size. Ever.

So:

The iPhone's camera lens has a focal length of 4.1mm. The field of view of that lens is equivalent to that of a 33mm lens on a full frame camera.

If you don't shoot with a FF camera, then I'm not sure of what value this information is.
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Old Dec 3, 2012, 06:30 PM   #5
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Right, that's what I was getting at. I was just trying to get a comparison for field of view. Mostly out of curiosity. Thanks.
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