This is one of the hot topic in the google related to iPhone LED and Camera issue. This seems to be very common for most of the iPhone models 4,4s,5,5s.
There are lot of reasons for Camera/LED not working
– Software related settings
– Hardware failure
– Dust and Water Damage
– Third Party Apps in JB Phone can interrupt the camera functionality.
In my case, when i open the stock camera app, the screen went to black and screen doesn’t respond. When i switch to front camera it works good. This might be related to some hardware related issue. Went head and opened the back lid using the 2 precious bottom screws of the iPhone 4 to see what went wrong.
The Camera unit is occupying a very safety place and to unplug we need to remove the battery, logic board and the other connectors going through the unit. I don’t want to mess up the board and logical unit as i can live with front camera. So, smoothly tilted the rear camera app upwards and again pressed them back to the seat rest.
Restarted the Phone and did a restore of the Cydia Apps. The rear camera started working again. Earlier i tried a lot of videos, articles and nothing helped.
This fix may work for you only if your camera and led both fails to work and you are seeing a black screen in the camera app.