An industry source revealed an interesting detail about vivo’s upcoming X60 trio. Apparently it will become the first smartphones to use pixel shift technology. You may have heard of pixel shift as it has been used in select DSLRs in the past, but never on a phone.
Interestingly, the vivo X60, X60 Pro and X60 Pro+ are already official in China and there hasn’t been a mention of such camera technology. Then again, the Chinese versions of the X60 and the Pro use Exynos 1080 chipsets and (according to rumors) the global versions will switch to Snapdragon 870 instead (the Pro+ will keep the S888, of course). So, the March 22 event will be more than just a global launch for the X60 series.
What’s pixel shift, anyway? To answer that first we must look at how digital camera sensors work. Most use a Bayer pattern – unlike a display where each pixel has multiple sub-pixels with different colors, a single pixel on a sensor sees only one color. Red, Green and Blue pixels are arranged (usually) in the Bayer pattern, which is a sort of three color checkerboard.
But that leaves gaps in the color data, huge gaps. The Green channel covers 50% of the image, Red and Blue channels only get 25% coverage (the human eye is most sensitive to green). Interpolation is used to fill in the gaps, but that introduces inaccuracies. This illustration should help you visually understand this interpolation called “demosaicing”.
There’s another way – shift the sensor, side to side and up and down one pixel at a time. This allows the sensor to fill in the gaps and get 100% coverage on all color channels. The illustration below shows an idealized example. It and the one above we borrowed from Google’s explanation of pixel shift based super resolution (more here).
The way Google did it for the Pixel 3 was to depend on your hand’s natural hand shake (carefully counterbalanced with the OIS system) to move the sensor around. Several shots are taken and then they are aligned by clever image processing algorithms. That’s one way to do it.
But from what we’re hearing it is not how vivo is going to pull it off. Instead, the company will leverage the unique gimbal system to move the sensor around. The advantages of this are one, it’s more precise, and two, it also works on a tripod (Google’s approach clearly does not).
There will certainly be a detailed explanation during next week’s event. But the details we got indicate that the X60 phones will shoot 8 RAW images, pick the best one and use information from the other 7 images to fill in the gaps.
The result is a single photo where every pixel has true color data instead of having two interpolated channels. This should create more detailed images with better color accuracy to boot.
Our source tells us that all three vivo X60 phones will feature pixel shift technology. Note that basic pixel shift requires only 4 shots, but vivo will take 8 shots. This suggests sub-pixel rendering may be employed, which increases the resolution of the final image. This could be a boon for digital zoom.
If the static images above didn’t do a good enough job of explaining, maybe Sony’s video about Alpha 7R IV that shows the concept in motion will be easier to understand. The good stuff starts around 30 seconds in, we’ve cued it up:
Note: pixel shift shouldn’t be confused with sensor shift, which is an image stabilization technique (an alternative to OIS).