Press and HOLD both Vol Up/Down buttons. Keep holding while the screen goes fully black (ignore the screenshot), keep holding through the Black/White logo and when the Colored Logo shows up, release those buttons.
If you have the STL100-1 variant the volume button reset method doesn't work. In that case, Press and HOLD the Power On Button until you see the LOGO as above
Did you recently load any new apps, particularly apps or android apps that might use the camera? If so, you might want to UNinstall them - using Device Monitor (not just holding on the icon until blinking and then hit the garbage can icon)