iPhone 6s and iPhone 6s Plus announcedbyTimCook
Apple CEO Tim Cook announces the iPhone 6s and iPhone 6s Plus Reuters

Apple has announced the iPhone 6s and iPhone 6s Plus, a pair of smartphones with screens that know how hard you are pressing them. The handsets run Apple's new iOS 9 operating system and also feature upgraded cameras that can take higher resolution photos than any previous iPhone.

The phones were revealed at a press conference hosted by Apple at the 7,000-seat Bill Graham Civic Auditorium in San Francisco. Closely resembling the year-old iPhone 6 and iPhone 6 Plus, the new models follow in the footsteps of the 4s and 5s by retaining the aesthetics of their predecessors, but offering new internals. The new iPhones' TouchID fingerprint scanner is claimed to be twice as fast as that of their predecessors.

As well as a new 64-bit A9 processor – alleged to be more energy-efficient and 70% faster than last year's A8 – Apple has given the new iPhones a 12MP rear camera, up from the 8MP snapper of the iPhone 6. Both phones are capable of shooting 4K video with their rear cameras, as well as 63MP panorama photos. Front camera sensors have been boosted from 1.2MP to 5MP.

What is Apple 3D Touch?

First seen as Force Touch on the Apple Watch and new MacBooks, 3D Touch is a technology where the screens of the new iPhones know how firmly they are being pressed. A simple tap performs one action, but press harder and a second action is available.

Capacitive sensors integrated into the back light of the iPhone's screen monitor how much pressure is applied by each finger. The vibration motor (or haptic engine, in Apple speak) has been upgraded to start and stop more quickly. The motor can spin up to full power in a single rotation, and back to zero just as quickly. This means the iPhone 6s can produce a wider range of haptic feedback; the shortest lasts for just 10 milliseconds. These subtle vibrations help to make navigating through iOS 9 feel more physical and tactile.

Pressing firmly on links within messages or emails lets you 'peak' at what content is delivered by that link – check a web page or image linked in a message without opening it all to view it in full screen. A firm swipe from the edge of the screen lets you swipe between open applications without going via the multitasking menu.

3D Touch is open to third-party applications. A firm press on the app's home screen icon can, for example, let you change your social network status (to Busy, for example) without opening the app itself.

Aside from 3D Touch, the iPhones' displays remain unchanged from last year. That means the iPhone 6s and 6s Plus measure 4.7in and 5.5in respectively, have resolutions of 750 x 1334 and 1080 x 1920, and pixel densities of 326 per inch and 401 per inch. These stats are starting to fall some way behind Apple's rivals – the Samsung Galaxy S6 has a pixel density of 577 per inch, while the newly announced Sony Xperia Z5 Premium has 806. But pixel count is not everything and we will be keen to see how all four handsets compare when we put them head-to-head over the coming weeks and months.

Bye bye, Bendgate

The iPhone 6 Plus caused headlines when some owners found it would bend out of shape if left in a particularly tight jeans pocket. To fix this, Apple has produced the iPhone 6s and 6s Plus from a tougher grade of aluminium. With an infusion of zinc, 7,000 series aluminium is stronger than any metal used by Apple before.

iOS 9

iOS 9 on iPhone 6
iOS 9 for the iPhone 6s and older models includes an improved Siri, public transit directions, and more Apple

As is tradition for Apple, the new iPhones will go on sale with the company's latest mobile operating system, this year called iOS 9. Revealed back in June, iOS 9 has a host of new features that will be coming to older iPhone and iPad models in due course. Highlights include an enhanced Siri with 'Proactive', a system where the personal assistant can, for example, offer music playlists based on where you are, such as the gym.

Public transit directions will make a very welcome return, having not featured in iOS since Apple parted ways with Google Maps in 2012, in a refreshed and improved Maps app. iOS 9 will be available to download from 16 September.

Rose gold

To match the Watch Edition, Apple has added a new colour to the iPhone lineup: rose gold. Unlike the hugely expensive Watch Edition, this iPhone isn't made from actual gold, but will be merely coloured to match two new additions to the Watch Sport range in regular gold and rose gold.

iPhone 6s price, pre-order and release date

The iPhone 6s and 6s Plus will open for pre-order on 12 September, then go on sale on 25 September. Prices are the same as they were for the 6 generation, with the same storage options of 16, 64 and 128GB.