Dual Camera Smartphones

What are Dual Camera Smartphones?

A dual camera smartphone contains 2 cameras on the back, front or at both places. Not all dual cameras are the same and different setups are used on different devices and perform different functions. Dual cameras do not always mean better photos. There exist the following types of dual camera setups:
Stereo camera setup
Telephoto lens
Wide-angle lens
Monochrome sensor
Depth sensor
Periscopic lens

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A dual camera smartphone is a smartphone with 2 camera sensors instead of the conventional single sensor for the primary(back) or secondary(selfie) camera. Dual cameras are used for a variety of purposes which include achieving lossless zoom, 3D photography, fancy effects like portrait mode.

What are the different Dual Camera Setups and what are they used for?

Stereo camera(normal+normal)

LG Optimus 3D, The first dual camera phone

In this type of setup, the two sensors are placed at a considerable distance from each other(the digital stereo baseline varies from device to device) and are allowed to capture an image from two different angles, thus simulating the human eyes' vision. This kind of setup is particularly used for 3D imaging.Stereo cameras are the first type of dual cameras used in smartphones although this setup is not used anymore to capture 3D images, instead they are used for AR emulation. Phones using such a camera include the LG Optimus 3D and HTC Evo 3D.

Telephoto lens(wide-angle+telephoto)

This type of dual camera setup uses a wide-angle lens in one camera and a telephoto lens in another. Telephoto lenses have a longer focal length and show a magnified image with a narrower field of view. Smartphone cameras are small and cannot accommodate enough lenses to create optical zoom, digital zoom on the other hand leads to loss of quality and pixellated images. Telephoto lens setups overcome this shortcoming by providing a lens that is permanently zoomed in while the other is permanently zoomed out. Thus closeup shots are taken by the wide-angle lens and zoomed shots are taken by the telephoto lens achieving a greater level of lossless zoom. Portrait mode or bokeh shots can be achieved with this setup if both lenses shoot simultaneously with different apertures and with some software touchups. Telephoto lenses are used in the Apple iPhone X, Oneplus 5 and Xiaomi MiA1.

error_outline Smartphones using the telephoto lens setup have a wide-angle lens along with the telephoto lens but here, the focal length of the wide-angle lens is quite low and thus acts similar to regular lenses. In other words they are not as wide-angle as the sensors in the next setup.

Comparision between telephoto, normal & wide-angle lens

Wide-angle lens(wide-angle+normal)

Much like the last one, this setup has a regular lens and a wide-angle lens. Wide-angle lenses have a substantially smaller focal length, thus having a greater field of view. This setup is used to capture wider shots. Cameras with this setup don't involving using both sensors at the same time and the user can switch between them. Some phones using such a setup include the LG G6 and Oppo F3.

Monochrome sensor(normal+black&white)

Monochrome+RGB setup

In this type of camera setup one lens is a standard RGB(Color) sensor whereas the other one is monochrome(Black and white). The idea behind this arrangement is that shadows and depth can be more accurately captured by a monochrome sensor. Thus the image is taken simultaneously in both the sensors and are morphed together to enhance the depth of field. This camera setup requires a lot of software enhancement to create a good quality image. Phones like the Motorola Moto G5S Plus and Huawei Honor 8 Pro have such a camera setup.

Depth sensor(normal+normal)

This kind of camera setup is mostly found in entry level phones and is similar to the Stereo setup, but is used for a different purpose. In this setup there is normally a difference between the resolutions of the sensors. Photos are taken simultaneously from both cameras and merged in a way that the subject(Person or object being shot) is captured by the high resolution camera and appears clear whereas the background and depth of field is captured by the low resolution(Depth sensing) camera and appears blurred, thus trying to provide a portrait mode like effect. This is a cheaper alternative for users for whom, effects are most important. Devices like the Oneplus 5T and Lenovo K8 Note use this setup.

Periscope lens(normal+periscopic)

Oppo 5X

This technology has been ingeniously designed by Oppo and dubbed as "5X dual camera zoom", in this besides a regular camera sensor, the second sensor is sideways. With this setup, they promise to provide 5X optical(Lossless) zoom in a smartphone camera by placing the sensor and lenses horizontally and reflecting the image to it with a prism. The advantage of this setup is that a large number of lenses can be accommodated without increasing the camera bump. Although only one prototype has actually been made to accommodate such a setup it is a very great concept and may be commercially used soon.

Are Dual Cameras always better than a single one?

Not necessarily, although dual cameras normally produce good images, without good sensors, lenses or software they are useless. Dual cameras have nowadays also become a marketing gimmick nowadays. So in order to get good images, good implementation is necessary which cheap smartphone manufacturers sometimes ignore as the 2 lenses are enough to get their devices sold.

Devices Like the Google Pixel 2 and the HTC U11 are examples of the best camera phones in the industry even when they only have a single camera. Thus good software, hardware and implementation in a single camera might produce better quality images than dual cameras.

But for now the future of dual cameras looks bright as they are appearing on more and more devices and their designs are constantly being refined. They definitely seem to be the future of the camera phone industry.