Huawei P30 Pro cameras explained: 5x zoom and better low-light shots through optical wizardry

To be clear, the telephoto camera on the Huawei P30 Pro has a fixed lens, so it only does 5x zoom relative to the main camera. If you zoom in at 2x, for example, that's going to be digital zoom from the main cam. Interestingly, in the range between 3x and 4.9x zoom, the phone uses both its main and telephoto cameras to capture visual information, which should result in more detail. In the range between 5x and 50x, only the telephoto camera is used, with all zooming beyond 5x done digitally.

Huawei's RYYB color filter explained

Of course, most of the time when shooting with the Huawei P30 and P30 Pro, you'll be using their main, 40MP camera. What's unique about it is that it uses a different color filter, resulting in 40% better light absorption compared to the sensor on the P20 Pro.

To explain how such a considerable gain is achieved, we need to shed light on how digital imaging works. You probably know that a typical modern display is made of pixels, and each of these pixels has a red, green, and a blue subpixel. Colors are produced by blending light from these subpixels, allowing each individual pixel to produce any color we want. But camera sensors are different. They do have pixels as well, but a single pixel can't capture any color on its own. Each pixel has a filter over it allowing only red, green, or blue light to pass through. These color filters are arranged in a pattern and are collectively called a Bayer filter (invented by Bryce Bayer of Eastman Kodak some 43 years ago). 

On one hand, the Bayer layer allows each pixel of an image sensor to capture full color. A pixel already captures one of the three primary colors, and values for the other two primaries are estimated from its neighbors. However, a significant amount of light is blocked in the process. 

Most image sensors have color filters arranged in a red-green-green-blue (RGGB) pattern, but Huawei's 40MP sensor swaps all green pixels with yellow ones (hence, the RYYB abbreviation mentioned above). Since yellow light is made of green and red light, a yellow filter lets more light pass through, which is how the gain in light absorption is achieved. And the value for green light is estimated by subtracting that of the neighboring red pixels. 

So, this seems like a super simple trick to boost a camera's performance. Why has nobody thought of it before? Well, as a matter of fact, experimentation with alternatives to the classic Bayer filter has been going on for decades. Nikon and Canon are known to have used CYGM filters (cyan, yellow, green, magenta) in their cameras, but while this filter may have better dynamics range, it lags in terms of color accuracy. Another example would be the first-generation Motorola Moto X which used a RGBW (red, green, blue, white) filter to let more light through, but again, its camera didn't stand out in any way with its image quality. Some phones, including a number of Huawei flagships, had multi-camera setups where a color camera was paired with a monochrome one with no filter at all. Visual data from both was combined to produce a superior image. It's a trend that's fading out.

The classic RGGB color filter, however, remains the most widely used as it is old, familiar, thoroughly tested tech. It is easier to implement and the images are easier to process. We applaud Huawei for trying something new – for going through all the trouble that implementing a new color filter requires (and there's more of it than one might assume). But only time – and more thorough camera testing – will tell if Huawei's color filter truly outperforms the classic Bayer filter in every way.