Dual Camera in a Smartphone
Before diving deep into the specific that how it works, we first need to understand why the manufacturer realize the need of two rear camera in a smartphone. Though the trend is started at this year MWC in Barcelona, it was first introduced by HTC in EVO 3D in the year of 2011. It was the first phone capable of recording 3D video.
Previously smartphone comes with fixed focal length. Thus we need to rely to digital zoom to close down a picture. As the digital zoom is Megapixel resolution dependent, there will be variation in the quality of the zoomed picture. These limitation results in the implementation of optical zoom in the smartphone cameras.
Optical Zoom vs Digital Zoom
Optical zoom works by lens adjustment whereas the digital zoom is done after taking photo i.e. inside the camera. It depends upon the image processing capability of the camera. Thus optical zoom is not resolution dependent like the digital zoom.
If a digital camera is 12MP and it has 10x optical zoom with focal length 50-250mm, then at 50mm your image is 12MP and at 250mm it is still 12MP. In case of digital zoom the resolution decreases as you zoom in more and more.
What is Telephoto lens
Generally Telephoto lens is said to be having a long focal length but actually the physical length of the lens is shorter than the focal length.
In case of dual camera smartphone the second one uses a telephoto lens. The primary camera used for same work whereas the secondary one takes care of clarity of the image and zooming feature. Sometimes it captures the depth of the field.
A camera having a 18mm focal length and another with 27mm, giving us 1.5xnoptical zoom. So as in the IPhone 7, Apple offered one 28mm and one 56mm lens, giving us a 2x optical zoom. It means we can take close shot at 1x zoom and then by using the 2x zoom we can able to capture images at greater distance without any loss in the resolution.
Apple uses this feature most well in the iPhone. Recently Oneplus 5 and also Mi A1 comes up with the same technology. But still there is limitations in this with a fixed focal length. There it is unable to offer dynamic range like the DSLR lenses.
But without any hesitation this is a big step forward in the smartphone camera section. This has some great advantage like long distance quality zoom and that ‘Bokeh’ effect by blurring the background.