With more and more smartphones launching with a dual camera system, or two lenses on the back, we're taking a look at where this has all come from and romp through the history of dual lens smartphones. 

Dual lens cameras on smartphones aren't new, with a number of models offering a range of unique features using this camera setup, as far back as 2011.

Apple might be have brought it to the masses in 2016 with the iPhone 7 Plus, but follow us as we walk you through smartphones dual lens camera systems of the past and present and into the future.

In 2011, 3D was a thing. The world's TV manufacturers were lining up 3D TV sets, there were 3D films being produced and we were being told that 3D was the next big thing (again).

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For smartphones, it was the opportunity for innovation. The LG Optimus 3D was announced in February 2011 and the HTC Evo 3D launched on Sprint in March 2011. 

Both these smartphones (and there were some others) used dual lenses to allow them to take 3D video and 3D photos. They use the same technique used by regular 3D cameras, using those dual lenses to create a sense of depth in images. This was boosted with a 3D display to view those images, without the glasses. 

But 3D was just a passing phase, and although we could capture 3D, ultimately, that was only the start of the story for dual lens cameras.

It was the HTC One M8 that really introduced dual lens cameras to the world and saw HTC trying to do something different. The HTC One M8 was launched in April 2014 and very much used two sensors in the same way that modern smartphone cameras do.

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With a 4-megapixel UltraPixel main image sensor and a secondary 2-megapixel sensor capturing extra data, the dual lens camera was used, like 3D, to create a sense of depth in photos. The idea was that the second lens could capture this depth information to create a depth map and feed it into the final image.

That meant you could create bokeh/background blur effects, you could refocus the image with a tap and you could easily manipulate photos, keeping the subject sharp and changing the backgrounds, even after you'd taken the photo.

The One M8 was clever, but the camera wasn't that impressive. The effects were rather gimmicky and the benefits of having a dual camera didn't really make an impact - even if the full metal body did.

Step forward a few years and LG announces the LG G5 in February 2016. There are two things that are interesting about it. Firstly, it attempts to integrate modular accessories. Secondly, LG equipped it with dual cameras.

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In the case of this LG smartphone, there's a main 16-megapixel sensor and a second 8-megapixel sensor. Rather than combining information to create effects, LG's dual camera approach is straight shooting. The 16-megapixel camera offers regular photos, but the second lens is wide-angle. 

With 135-degree lens on the rear for that 8MP camera, the LG G5 could shoot wide-angle photos to great effect. You simply switch from one camera to the other by tapping the button in the app and you can get more in. Perfect for tight spots or landscapes, with that slight fish-eye effect that's on trend.

LG followed up the G5 with the G6 in April 2017, repeating the camera positioning again, but this time with two 13-megapixel cameras on the back, one with a 125-degree wide angle to again capture those super-wide photos.

With LG making its mark, Huawei launched the P9, in partnership with Leica, in April 2016. With two cameras sitting on the back, Huawei's big selling point wasn't about depth sensing or wide-angle, it was about monochrome.

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Leveraging Leica's classic monochrome cameras, the Huawei P9 presented two cameras on the rear, claiming one lens captured RGB colour and the second lens captured monochrome detail. Both cameras are 12-megapixels. 

This results in some great black and white photos, but working together, the P9 attempts to combine information from both sensors to make all your photos better. The results are very good, it's a very capable partnership. There's also a P9 Plus with the same offering, but slightly larger.

Step into 2017 and the Huawei P10 repeats the performance, but this time pairs a 20-megapixel camera with a 12-megapixel camera. It can still capture monochrome data, but also offers depth sensing, again designed to have a better idea of how to pick it the difference between the foreground and background.

With the Huawei P9 launched, it was only a matter of time before sub-brand Honor produced an equivalent model. Called the Honor 8, again, there is a dual camera on the back. 

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With the Leica tie-in being for the Huawei phone, the Honor 8 doesn't make much of the monochrome side of things, but again offers twin 12-megapixel cameras, one with an RGB sensor, the other with a monochrome sensor. 

The message is the same: data is combined to result in sharper images, with better grip on colour and monochrome detail. Again, the result is a camera that's very capable, especially on a phone that's purportedly mid-range. Honor expanded this to the Honor 8 Pro too.

Honor uses the formula widely in its phones, with the mid-range Honor 6X getting a 2-megapixel companion camera, and the Honor 9 stepping up to a 20-megapixel main camera.

The Apple iPhone 7 Plus features two cameras on the rear. Both are 12-megapixels, but they offer a different focal length. The first camera offers 23mm zoom, which is sort of wide - not super wide like LG, but wider than the old iPhone camera. Only the wide lens has optical image stabilisation.

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The second camera is zoomed at 56mm. This means that everything appears closer through this lens. It's like LG's pairing, but reversed. The idea, according to Apple, is to let you zoom without losing so much quality. To get closer to the subject you can switch to the 56mm camera and any digital zooming you then do is starting from a closer position, so the loss in quality will be slightly lessened compared to a regular smartphone camera.

Apple is also looking to play HTC's game by offering a portrait bokeh effect. This will aim to get you that blurred background effect that is created by shallow depth of field on DLSR cameras. Using information from both sensors it will create a depth map, keeping the subject sharp and blurring the background.

It's not just zooming and bokeh - those super consumer features - and need a dual camera setup on the back: welcome to Project Tango.

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Tango is all about a different kind of capture and experience which in many ways harks back to the 3D cameras we talked about at the beginning of this feature. Google's Tango project is about the phone knowing where everything sits in a 3D environment around it. Sound familiar? Yes, it's the basic principle behind a lot of AR (augmented reality) and VR (virtual reality) content. 

There are two phones that currently support Tango - the Lenovo Phab 2 Pro and the Asus ZenFone AR. Although you can buy these devices commercially, they are really developer phone, designed to help those working in this new world of mixed reality to create their applications and experiences. 

These phones are going to be used for things like 3D mapping of rooms, letting you scan a room and then use mixed reality to insert a new kitchen, for example, or to use real life capture that can then go into a virtual reality application.

Asus also has the Asus ZenFone 3 Zoom, another model with twin rear cameras.

OnePlus, the brand that touts the "flagship killer" has joined the dual camera fray with the OnePlus 5. This model packs in two camera on the rear, one with 16-megapixels and the other at 20-megapixels, offering both bokeh features and a method of zooming.

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The OnePlus 5 attempts to do everything with its dual camera configuration. There's depth sensing aiming to deliver better bokeh effects through the portrait mode, but there's also a play to zoom.

OnePlus refers to its cameras as wide angle and telephoto, with the 16-megapixel f/1.7 camera picking up the wide-angle business and the 20-megapixel f/2.6 camera for telephoto. OnePlus called this "2x lossless zoom", but in reality it's a 1.6x optical zoom from the lens, with a 0.4x coming from smart multi-frame capture. Essentially, it does the same as the iPhone does.

Nokia's flagship phone, the Nokia 8, also has a dual camera configuration on the rear. This gives you a pair of 12-megapixel cameras developed in partnership with Zeiss, with one lens capturing RGB data and the other monochrome data. Yes, it's the same idea as Huawei has with Leica.

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Here you have two 13-megapixel cameras, f/2.0, working together to gather information with the aim of increasing the quality of your photos in any conditions. 

But Nokia can't avoid the bokeh bandwagon, using the sensors to gather depth information that can be put to use in portrait photography, blurring the background with a "live bokeh" function.

The Samsung Galaxy Note 8 is the first Samsung phone to offer a dual camera. It also makes another "first" move, offering optical image stabilisation on both of its cameras.

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The configuration that Samsung has opted for its basically the same as the iPhone 7 Plus, except it has specced up the cameras a little higher. The aperture on both is a little wider and having both offering OIS should lead to come nice stable images.

There's also a range of supporting features outside of the 2x zoom offered by the second lens. There's live focus effects letting you change the bokeh on your portraits and you can also snap from both cameras at the same time using Dual Capture. That gives you two different perspectives on the same subject.

So far, pretty much all these lens arrangements have been the same, i.e., the sensor faces out the back of the phone with the lens in front. But there could be another way to flip this around.

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Oppo showed off a prototype of an alternative method of arranging the cameras on the back on the phone. Presently, the limitation is the thickness of the phone, as that only gives you limited space in which to work. Oppo's solution is to flip the telephoto camera 90 degrees and use a mirror, like a periscope, to bring the light path into line.

The advantage this offers is that you are not limited by the thickness of the phone, because the lens array is running at 90 degrees. Yes, you need internal space to accommodate this solution, but you could end up with greater optical zoom because you have more space for the lenses. The prototype we've seen looked impressive in its performance. But how much zoom do you really need from a phone, and as the zoom increases, how do you stabilise it?

The future? Perhaps.