More than 150 filmmakers and photographers — including Alex Gibney (Going Clear: Scientology and the Prison of Belief), Kirsten Johnson (Cameraperson), and Laura Poitras (Citizenfour) — have signed a letter calling on manufacturers including Canon, Fuji, Nikon, Olympus and Sony to build encryption features into still and video cameras.

The open letter, published by the nonprofit Freedom of the Press Foundation, claims that new security features are necessary to protect the safety of filmmakers, who may legitimately fear the seizure of their cameras by hostile authorities, as well as that of their subjects, who could face repercussions for their appearance in unencrypted interview footage.

"On countless occasions, filmmakers or photojournalists have seen their footage seized by authoritarian governments or criminals all over the world," the letter says. "Because the contents of their cameras are not and cannot be encrypted, there is no way to protect any of the footage once it has been taken. This puts ourselves, our sources, and our work at risk."

The letter cites Windows and Mac computers and Apple's iPhone as well as secure apps including WhatsApp, iMessage and Signal as examples of technology that protects communication from end to end. While photo and video content can be encrypted as soon as it is stored on a PC or mobile device, it's the time frame between acquisition of sensitive footage and the shooter's ability to transfer it from unencrypted storage that generates anxiety for filmmakers.

"Encryption features will allow us to continue to tell the most important stories, from some of the most dangerous places in the word. You can help us reach that goal by starting to work towards building encryption into your camera products," the letter concludes.