Why would my iPhone 5s camera screen be completely black and not take photos?

[iMore Question]

When I click on the camera icon, it gives me the camera screen but it's totally black. It does absolutely nothing to take a photo but will allow me to look at previously taken photos.

 

[Just_Me_D]

I don't know. Is something covering the camera lens? Have you tried rebooting your device?

 

[kataran]

Reboot it happened to my 5s before