In Hong Kong's largest protest camp, the "No Photo" signs are posted everywhere. Many of the demonstrators are living at the camp, in the city's central Admiralty district.
"We're all anonymous heroes," read a typical sign. "No close-ups on faces, please!," said another.
Undercover policemen are thought to patrol the camp regularly. Some worry that officers have been collecting legal evidence that will eventually be used to prosecute the protesters.
So, when a group of friends working in a local photography studio set up an outdoor photo booth, a simple yellow backdrop situated in front of a camera, it was feasible that many would have avoided it.
Instead, hundreds have lined up to have their portraits snapped and then posted on Facebook.
More than 1,200 photos have since been uploaded to the group's page, Yellow Backdrop HK.
"We wanted to use what we know to get involved in this movement, to let people know what is happening here. Because in the news, people will see some violent actions involved and maybe in our photos, we show other faces of the people here," explained Max Wong, one of the organisers.
'Yellow is the colour'
For over a month, thousands of protesters have been living in tents in downtown Hong Kong, demanding changes to the territory's election laws.
They want the right to nominate their own candidates running for the position of chief executive in 2017, instead of allowing Communist leaders in Beijing the chance to vet the candidates.
Recent photos posted to the photography group's Facebook page showed a wide range of Hong Kong citizens, including university graduates dressed in ceremonial robes and a young mother with an infant strapped to her front.
"Yellow is the colour of this movement, it symbolises freedom and hope. The simple backdrop represents the pure motive on pursuing democracy, freedom and just society," the group said on its Facebook page. "We hope these pictures will help the world know the belief behind every beautiful face."
In smartphone-centric Hong Kong, snapping a photo might seem trivial.
But at this camp, stepping in front of the yellow curtain and the camera's lens is just one more act of defiance, an act of courage.