I've never had much success with Touch IDin my iPhone 5S. While Touch ID worked well initially, my fingerprints seemed to "fade," gradually becoming unrecognized within a week or two. Invariably, I'd delete them, scan them again, and they'd work for a couple of weeks before fading again.
Friends and followers that I queried about their Touch ID accuracy claimed near-perfect results, so I chalked my experience up to dry skin or some other problem with my subdermal ridge flow angle mapping – a "lossy process that discards minutia data that would be required to reconstruct the user’s actual fingerprint" according to Apple's iOS Security white paper (PDF).
When iOS 7.1 was released on March 10, Apple noted "Improves Touch ID fingerprint recognition" way down in the release notes. When I read this I anxiously deleted and re-scanned all of my fingerprints and sure enough, my accuracy improved dramatically. For about a month or so.
I have the best luck with Touch ID when I scan my right thumb (my primary unlocking digit) five different times and when they start to fade (every month or so) I delete and re-scan my prints again.
When iOS 7.1.1 was released on April 22, Apple noted "Further improvements to Touch ID fingerprint recognition" as the first of only three features mentioned in the release notes. Again, I couldn't wait to test the "further improvements."
In typical fashion, Apple didn't provide any details about the specific improvements to Touch ID in iOS 7.1.1, but a poster to both Reddit and The Verge forums claims to have gleaned some details from a source that "works with Apple hardware."
With iOS 7.1.1 Apple now takes multiple scans of each position you place finger at setup instead of a single one and uses algorithms to predict potential errors that could arise in the future. Touch ID was supposed to gradually improve accuracy with every scan but the problem was if you didn't scan well on setup it would ruin your experience until you re-setup your finger. iOS 7.1.1 not only removes that problem and increases accuracy but also greatly reduces the calculations your iPhone 5S had to make while unlocking the device which means you should get a much faster unlock time.
iOS 7.1.1 reads my fingerprints perfectly and while I can't confirm that iOS 7.1.1 "greatly reduces the calculations your iPhone 5S has to make," it seems to scan them a little faster than iOS 7.1 did. Having only been out for two days, it's too early to say whether iOS 7.1.1 will fix my particular Touch ID issues, but it's definitely off to a good start. I'll update this post if I hear back from Apple and if my prints last longer than a few weeks without fading.
Now let's hope that Apple exposes a Touch ID API to third-party developers so that banking and payments apps can take advantage of this promising new technology.
More technical information on Touch ID can be found on pages 6 and 7 of the iOS Security white paper.