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(Pocket-lint) - Apple just unveiled its “best iPhone yet” (we were waiting for the quote to drop too) and it comes with a more advanced camera proposition than its predecessors.

But this time there's a key difference between iPhone 7 and iPhone 7 Plus: the latter coming with dual cameras. So what's the deal and what can dual camera tech offer?

Apple iPhone 7 Plus dual camera explained: Wide-angle and 2x tele

We've seen dual cameras before in devices, from the LG G5's wide and super-wide lenses, to the Huawei P9's colour and monochrome sensors.

The iPhone 7 Plus does things differently: the first camera is a 23mm (equivalent) wide-angle, which is wider-angle to fit even more into the frame than the previous iPhone 6S's 29mm (equivalent).

The second lens, which is absent in the standard iPhone 7, offers double the focal length, to act like a 2x multiplier; a 56mm equivalent. That's the opposite direction to other manufacturers, which is an interesting take, making far-away subjects look closer-up in the frame compared to most wide-angle camera experiences.

Apple iPhone 7 Plus dual camera explained: Zoom potential

The tele lens option - although it's a bit of a stretch to call it that - will resolve greater detail than simply taking a wide-angle shot and then zooming into it, which is where another one of its strengths lies: digital zoom.

Beyond the 56mm optic, Apple will offer up to 5x digital zoom (sold as 10x from the wider-angle lens), but the fidelity will be better than wider-angle equivalents. It'll still be subject to the same limitations of digital zoom, but we can see why Apple is claiming it will be that much better.

Apple iPhone 7 Plus dual camera explained: Portrait bokeh

Pro photographers love their background blur, known as bokeh, which depends on wide apertures (and subject distance and focal length, to varying degrees) to produce that soft background and popping subject depth.

Now Apple wants to extend bokeh to the masses (or fauxkeh, given that it's digitally produced) by using both the iPhone 7 Plus's cameras in one. The 23mm (equivalent) wide-angle lens can be compared to the 56mm (equivalent) tele lens to create a depth map, with close-up subjects rendered in focus, more distant objects out of focus and the faux effect added.

We're yet to see any manufacturer produce a perfect bokeh in post-production - HTC, Huawei, LG and more have certainly tried - so Apple's limiting of this effect to its new Portrait mode may limit its potential to slip-up. We'll have to wait and see as the software won't be out until later in 2016.

Apple iPhone 7 camera details explained

Only the iPhone 7 Plus has that 23mm (equivalent) lens, with an f/1.8 aperture - which is brighter than the iPhone 6S's f/2.2 aperture by a full stop and, therefore, lets in 50 per cent more light than last time. It's not the brightest lens on the market - Samsung already offers f/1.7 on its latest Galaxy phones - but will mean greater control and better low-light results than before.

Both cameras also offer optical image stabilisation for the first time - that was reserved for solely the Plus model previously, but is now found on the "standard" iPhone 7.

With the iPhone 7 Plus the second 56mm (equivalent) lens has an f/2.8 aperture. If it was any wider (say, f/1.8 also) then the physical size would be to excess. It's still plenty bright.

Apple iPhone 7 camera: New signal processor

The sensor in the iPhone 7 and 7 Plus is 12-megapixels, which Apple describes as “an entirely new camera”. But it doesn’t detail whether it’s the same base unit as the 1/3in size (1.22µm pixels) one in the iPhone 6S or not.

The key difference in the iPhone 7 is the addition of new image signal processor (ISP). It’s twice as rapid as before in its ability to read the scene and, therefore, decide how to respond with focus, tone, noise reduction, colour and so forth.

This approach is something camera manufacturers often utilise between generations of camera upgrades. It means marginal gains in image quality from a processing point of view.

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We’ll be receiving both iPhone 7 and 7 Plus models following Apple’s press event in San Francisco, so we’ll be bringing you results through reviews, previews and features over the coming days and weeks - keep eyes on the site for further insight.

Writing by Mike Lowe. Originally published on 7 September 2016.