[metmom]

That is amazing.

[Steely Tom]

I did a quick calculation to see how reasonable this idea is, and was surprised by the result.

The resolution of the iPhone 7's wide-angle camera is approximately 4600x2600 pixels with a field-of-view of about 63 degrees width; this translates to an angular resolution of about 240 microradians per pixel.

It's surprisingly difficult to find hard numbers giving the distance between fingerprint ridges and grooves, but I was able to come up with a estimate of 0.05 mm (50 microns) for the closest spacing after some looking.

At one meter distance, this is 50000 microradians per pixel, which means that at distance of one meter, the iPhone wide-angle camera can put almost 210 pixels on each pair of ridges!

This makes the article's claim believable, although getting enough contrast on a fingertip to pick up individual ridges and grooves is questionable; with optical contrast only (no ink or surface-contact effects) a great deal of dynamic range would be required to obtain a fingerprint of sufficient quality to do personal identification.

Still, it's only a matter of time before this is possible.

[Steely Tom]

Sorry, that calculation was way off. When I looked at my write-up on the screen, it just didn’t look right.

Looks like I’m off by a factor of a thousand (swapped meters for millimeters at one point).

It’s actually 0.21 pixels per ridge spacing at one meter, which puts it out of reach of the iPhone 7 camera. Way out of reach, even if you don’t count the dynamic range issue.

I should have double-checked.