With its bigger screen, better wireless, a faster processor and higher-resolution camera, we take a look at the important changes to the iPhone 5. See also: Apple iPhone 5 hands-on review
iPhone 5: the 4-inch screen
Although it retains the familiar look and feel of both the iPhone 4 and 4S, the iPhone 5 now has a 4-inch, 16:9 screen with a resolution of 1136x640 pixels. This means the screen is 176 pixels taller than the 4 and 4S, allowing an extra row of icons on the iOS Home Screen.
The change in height, not width, Apple says, is because it fits your hand better. It's clear, though, that there's pressure from other smartphone manufacturers to increase the screen size. Indeed, four inches is small by today's standards: Nokia's forthcoming Lumia 920 will have a 4.5in screen, and the Galaxy S3 feels gigantic with its 4.8in display.
See also: iPhone 5 launch video
The iPhone 5's display is more advanced than simply extra pixels. It has a built-in digitiser, removing a layer and enabling Apple to make the iPhone 5 thinner. Previously, the touch-sensitive layer was separate and laminated to the screen in the iPhone 4 and 4S.
Apple says this means the iPhone 5's display is clearer than ever (it still has the same 326 pixels-per-inch density as the 4 and 4S), and has 44% more saturated colours. There's no change to brightness and contrast though, with a claimed 500cd/m2 maximum brightness and 800:1 contrast.
All of Apple's apps will be updated to use the extra pixels, and we expect most developers to release updates for their third-party apps shortly after the iPhone 5 goes on sale on September 21st.
iPhone 5: dimensions and construction
The iPhone 5 measures 124 x 59 x 7.6mm, and weighs 112g. This compares to the iPhone 4S's dimensions of 115 x 59 x 9.3mm and 140g weight.
It's available in black and white versions, but the back design has changed. There's now a contrasting matt and gloss finish, since the panel is now primarily made from series 6000 anodised aluminium with glass inserts at the top and bottom. The black version of the phone has a darker metal band than the white version, which sticks with the same silver colour as before.
iPhone 5: iOS 6
The iPhone 5 will ship with the latest version of Apple's mobile operating system. iOS 6 includes plenty of new features, which you can read about in our separate iOS 6: what you need to know article. It includes a more capable Siri voice assistant, new Apple-designed Maps, a new Passbook app for tickets and coupons, integration with Facebook, shared Photo Streams, improved email, phone and internet browsing features.
iPhone 5: wireless
One of the other big updates is that the iPhone 5 will support 4G in the UK. You'll likely pay a premium for a contract which gives you mobile data via 4G, though, and carriers such as EE and 3 are yet to announce pricing. Due to its design, it won't support O2 or Vodafone's 4G networks.
Download speeds over 4G are up to five times faster than 3G, which the iPhone 5 also supports. Depending on who you buy an iPhone 5 from, you may or may not get the option of 4G data, with many networks only able to provide 3G, at least for now.
The network provider will also have to supply a new nano SIM, which is smaller than the micro SIM used by the iPhone 4 and 4S.
Wi-Fi has been improved in the iPhone 5, with a dual-band 802.11n radio. This means it can connect on either 2.4GHz or 5GHz with compatible hotspots and wireless routers. Using 5GHz is both faster and more reliable than 2.4GHz, primarily because the 5GHz band isn't yet widely used so fewer devices are competing for the bandwidth.
There's also the latest version of Bluetooth, 4.0, which is the same as the iPhone 4S.
Interestingly, Apple has decided not to include NFC in the iPhone 5. NFC is used in the Samsung Galaxy S3 and Nokia Lumia 920 to pay for purchases and share content between devices.
iPhone 5: storage capacity
There's a choice of 16GB, 32GB and 64GB models, meaning that the maximum capacity hasn't improved on the iPhone 4S. As before, there's no way to increase storage through the use of a memory card.
Next page: performance, cameras, ports and price
iPhone 5: performance
There aren't many details available on the new A6 processor, nor the amount of RAM inside the iPhone 5, but rumours suggest that it's a dual-core ARM Cortex A15 'system on chip' manufactured by Samsung. Apple says it's up to twice as fast as the A5 chip inside the iPhone 4S, and based on historical observation, that's likely to be true.
Again, there's no detail on the graphics chip built into the A6, but it's likely to be the same quad-core GPU in the new iPad.
We'll be testing and reporting on the iPhone 5's performance once we get our hands on a handset for review.
iPhone 5: cameras
As you'd expect, the rear camera has been updated to an 8Mp back-illuminated sensor. It's mated to a new, thinner, five-element lens with a sapphire crystal cover (rather than standard glass) for sharper, better-quality photos. Not only will the new setup improve upon the quality of the iPhone 4S's already brilliant photos, but it should produce better images in low light thanks to improved processing to remove noise. There's also an LED flash to help out in low light.
Photos are captured faster due to the quicker processor, and there's also support for capturing panoramic images as you sweep the iPhone 5 around. As long as you do it smoothly, it will produce a seamless 28Mp image.
Video-wise, the camera can also shoot 1080p video at 30fps, and has improved stabilisation compared with the iPhone 4S.
Audio hasn't been forgotten in all this, as there are now three microphones: one at the bottom as before, plus new front and rear mics to improve audio in both videos and also FaceTime calls.
The front camera, used mainly for FaceTime, is an upgraded model that's capable of 720p video and is good enough, Apple says, to inherit the iSight tag. This is used for cameras that can produce lifelike quality. It has been moved to a central position above the speaker.
Continuing on the improved sound theme is wideband audio support. As long as it's supported by the network provider, it means you'll get better call quality.
iPhone 5: ports and buttons
Buttons are virtually unchanged, with power volume and mute buttons all in the same positions.
The headphone jack, though has been moved to the bottom (something users won't appreciate if they want to connect a pair of headphones while the iPhone is docked). The iPhone 5 will ship with Apple's redesigned EarPods, which also act as a headset for calls thanks to a built-in microphone and control button.
There's also a new dock connector, named Lightning. It's much smaller than the old 30-pin connector and has a reversible design so you don't have to worry about which way you plug in the USB cable: it works both ways. It supports USB 2.0, but not the faster 3.0 standard.
Apple offers several adaptors so you can still use older 30-pin accessories: a basic adaptor for the eye-watering price of £25 and a Lightning-to-30-pin cable with an even steeper £30 price. In the box you'll get a Lightning-to-USB cable.
iPhone 5: price and availability
You can buy an unlocked iPhone 5 from an Apple store in the UK from 8am on 21st September. The base 16GB model will cost £529 inc VAT, but prices for the 32GB and 64GB models are yet to be announced.
There aren't yet any prices for the iPhone 5 on contract, but we expect mobile network providers to announce these shortly.