iPhone 5S and 5C: 10 things you should know

1. The iPhone 5S has a sapphire-covered home button. The laboratory grown, colourless gem is already used by Apple as a lens for the iPhone 5 camera. Harder than glass – supposedly only diamond is tougher – its scratch-resistant surface ensures marks don't interfere with the fingerprint scanner beneath.

2. The C in iPhone 5C stands for colour, not cheap. What was rumoured to be Apple's budget phone will in fact cost £469 out of contract, just £80 less than the top-of-the-range 5S. It will, however, come in pink, green, blue, yellow and white, so it's at least cheerful. Apple has designed contrasting cases with rows of small holes cut out of the back – maybe the C actually stands for Connect Four.

3. The iPhone now knows who you are. As rumoured, the 5S will be able to recognise you by your fingerprints. Touch the home button to unlock the phone, or make a payment on iTunes.

4. Apple won't keep a copy of your biometric data. The scanner converts fingerprint images into a digital signature that is then sent over the web. Apple says the scanner won't be available to third party app developers. It is encrypted, stored on the phone's chip, and not on its own servers or on the iCloud backup service. Which hopefully makes it snoop-proof.

5. The scanner can recognise more than one finger. The iPhone 5S can remember up to five prints, meaning you can use more than one digit to unlock the device, or give access to little digits, should you choose to share your phone with family members.

6. Both new phones have 4G. If you are prepared to pay the hefty contract price for a superfast mobile internet connection, both handsets are 4G-enabled for the spectrum bands used by the EE, O2, Three and Vodafone networks.

7. The 5S can do slow motion video. Record your film, then select the frames you want to slow down to quarter speed. Apple's show reel demonstrates how this comes in handy when you are crouching on a moving skateboard while filming a friend doing tricks on their stunt bicycle. Alternatively, quite good for You've Been Framed submissions.

8. Facetime now makes audio-only calls. Apple has redesigned its mobile software interface, the first big makeover since launch in 2007. One of the new features of iOS 7 is a big challenge to Skype. The video calls app, Facetime, will now be able to carry audio-only conversations – useful if the internet connection is too weak for video, or when taking a work call in pyjamas.

9. The 5S has two LED flashes – white and amber. Their intensity is variable, and a sensor decides which combination will give the best picture colour. To reduce blurring, in low light the 8 megapixel camera takes four photos in quick succession and merges their best bits.

10. The 5C and 5S go on sale from 20 September. The launch date for iOS 7 is 18 September. It will run on iPhone 4 and later models, iPad 2 and later models, the iPad mini and fifth generation iPod touch.