What is Sensor:

A Sensor is a hardware device, a part of camera which captures lights, converts incoming signals into binary numerical value and stores it. It determines everything of an image from resolution to image size, low light performance, dynamic range, depth of field etc. While talking about monochrome camera sensors, these are capable of gathering more details and sensitivity than would otherwise never be possible with color/RGB sensor. Here we will talk about Color vs Monochrome Sensors in dual camera setup.

Let’s take a deeper look on why monochrome sensors are less noise prone than RGB :

These days most of phone cameras comes with a dual camera setup. But each phone has a different kind of implementation for both cameras, something like below:

• One can be a wide angle RGB sensor and other is telephoto lens with RGB sensor, (Xiaomi MI A1).
• One can be with RGB sensor and other is monochrome, (HONOR 8).
• One RGB sensor with lowest of aperture like 1.7 or 1.6 and other RGB sensor can be with aperture 2.0/1.9 with same megapixel, (LG V30).
• One a normal RGB sensor and other one can be mere 2 MP sensor just to capture background details, (HONOR 7x).

Camera Implementations are different that’s why results are too.

Virtually every digital sensor works by capturing light in an array of photosites (A sensor is made of millions photosites), similar to a big buckets which can store rain drops. When the exposure process starts, each photosite gets uncovered to collect incoming light. When the exposure ends, each photosite read as an electronic signal which is further quantified, processed and stored as numerical binary value in a image file.

However, the above photosites only measure the quantity of light. To achieve color, photosites also need a way to differentiate and record each values separately for each color.

RGB or COLOR Sensor:

A necessary but undesirable side-effect of CFA’s is that each pixel effectively captures only 1/3 of incoming light, since any color not matching the pattern is filtered out. Any red or blue light that hits a green pixel won’t be recorded, for example.
These work by capturing only one of several primary colors at each photosite in an alternating pattern, using something called a “color filter array” (CFA), which uses alternating rows of red-green and green-blue filters.

Color vs Monochrome Sensors :

Unlike color sensors, monochrome sensors capture all incoming light at each pixel—regardless of color. Each pixel therefore receives up to 3X more light or 3X more exposure to a image, since red, green and blue are all absorbed:

Color Photosite

Monochrome Photosite

This transforms 1.5x more details and light sensitivity than what RGB sensor does. Unlike with color, monochrome sensors also do not require demosaicing to create the final image—the values recorded at each photosite effectively just become the values at each tiny pixel. As a result, monochrome sensors are able to achieve a slightly higher resolution than RGB ones.
Another advantage is, image noise is lower at equivalent ISO speeds, and resolution is higher. Such improvements in image quality can be critical whole shooting in low light.

Advantages of Monochrome Sensor:

Better low light performance with less noise.

Higher Resolution image with superior quality compared to Color Sensor

Helps to capture breathtaking B/W shots with good contrast and better exposure due to dedicated monochrome sensor.

FINAL SAY:

Hope I made it clear why these days mobile company uses monochrome sensor in dual camera setup to improve image quality.  They keep secondary camera with monochrome sensor and then combines both images (RGB + Monochrome) to get the better output. It also helps to capture some breathtaking B/W shots with good contrast and better exposure due to dedicated monochrome sensor. The quality of this B/W shot is way better than the one you will get with editing software.

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