I recently purchased a Nexus 6P 64GB, my first device from the Nexus series which is famous for it’s Stock Android experience. Everything was perfect with the phone, except the camera. The pre-installed camera application is obviously, the Google Camera. I noticed a slight flicker whenever I opened the Camera application in both Picture and Video mode. The camera flickered for a second, and then automatically re-focused and smoothed. There’s no flicker after that. To further investigate the flickering, I installed Snapchat on my phone, and tested the camera from it. Snapchat also had the same flickering just when I opened the application and then it disappeared.
I Googled up for this and finally found the reason for this problem in a post in the xda-developers forum. The flickering is due to the anti-banding filter trying to adjust to the frequency of the light bulbs (60 Hz in the US and 50 Hz in Europe). Some camera apps allow to manually set the filter (60 Hz, 50 Hz or Auto) but the Google Camera app seem to only allow auto filtering.
So the solution to the flickering is to install some other camera application from the Play Store which allows you to manually adjust the frequency filter to a value specific to your country.
I will search the Play Store for such an app and will update this post ASAP. If you find a nice alternative to Google’s Camera App with manual filter frequency setting, feel free to comment below.