A photographer focuses on Beijing's pollution to create a clear picture of the capital's murky air quality. Lin Qi reports.

Beijinger Zou Yi's morning routine includes snapping a daily photo of the Beijing Television station 150 meters outside his apartment window and tweeting the image to his Sina Weibo microblog.

He also posts a 3x3 grid juxtaposing the photo with those of the past eight days of the same building from the same angle. These reveal the fluctuating pollution levels, as some photos show skies that are cobalt blue and others that are leaden.