Dual camera is one of the hottest and the most talked about features in the smartphones today. Companies are trying different ways of implementing the new camera technology just to be unique and get a score up against their arch rivals. Clearly, it is the second lens, and what it does, which makes the whole thing truly interesting. While not all dual cameras are the same, one of the most interesting features in some of them is of the ‘optical zoom’.
And it is the ‘optical zoom’ which is where the things are getting interesting. While it might seem that achieving the optical zoom (in smartphones) is solely the duty of the secondary telephoto lens, it simply doesn’t work all the time. The ambient lighting condition plays a pivotal role in whether the secondary lens (with the smaller aperture) will work or not.
To demonstrate the same, we have a recently launched smartphone with us, the Xiaomi Mi A1. This phone has a 12 mega-pixel dual camera where the secondary lens is a telephoto lens (resulting in 2x optical zoom) with an aperture of f2.6. Its primary lens, on the other hand, has an aperture of f2.2 (smaller number means larger aperture).
Techno Tip: Larger aperture (smaller ‘f’ number) of a lens means that the lens is capable of taking more light in, which translates to better low-light images.
We clicked a number of pictures in 2x optical zoom, in mixed conditions, with the only intention of verifying when and where the telephoto lens does not work. To achieve this, we clicked same pictures twice – first with both lenses exposed, and then with the telephoto lens covered (simply by blocking it with a finger). Results are interesting nonetheless. Check below.
All the above images have 2x zoom. There is a visible difference in the two images in the first-three sets while the images in the fourth set are almost similar. It should be noted that the second image (without 2nd lens) in each set is clicked after the camera automatically switched to the primary lens because the telephoto lens is blocked.
The reason for the switch is that in low-light conditions, the telephoto lens with the smaller aperture doesn’t get enough light and hence, the primary lens (with the larger aperture) is activated automatically to do the job. Therefore, the zoom in the second images, in each set, is obtained through the primary lens and what we see is the digital zoom and not the optical zoom. This is because the optical zoom is the function of the telephoto lens only (first image in each set).
Also, in very good ambient light (outdoor), the camera refused to switch to the primary lens completely. When we covered the telephoto lens in these conditions, the view was simply blocked because there was no switch to the main lens. Hence, both the 2x zoom images below are the result of the telephoto lens and in this case, it is the optical zoom.
However, the camera in the Xiaomi Mi A1 is not the only one which works in this manner when it comes to the zoom. In fact, this is how the dual camera in the iPhone 7 Plus works already. Xiaomi has simply adopted the same functionality.
Our opinion on this subject is that the addition of an extra lens has given leverage to the phone manufacturers as to how they can accomplish certain tasks (in this case, zoom) given that there is a huge space constraint for cameras in a smartphone as well as limitations to technology while also keeping the market price more or less reasonable. It is a decent trade-off.