Unlike the iPhone 7, the iPhone 7 Plus actually has two 12MP camera sensors on the rear, offering both wide-angle and telephoto shooting options. The camera pair allows for 2x optical zoom and 10x digital zoom, but it appears that a hardware defect is causing the cameras to fail unexpectedly. Owners who attempt to use their camera in either Apple’s first-party Camera app or third-party alternatives are simply greeted with a black screen instead of a preview of the subject.
A thread over at reddit describes the issue, with teryakiwok writing, “I opened up the camera app only to be met with a black image preview, sometimes I can get an image however it's either tinted green or purple and was once accompanied by a screen stating 'Emergency iPhone needs to cool down' when the handset wasn’t even slightly warm.”
User tripler6 added, “I had this issue. Genius Bar said it was the shutter and replaced the entire phone. I was like.. iPhones don't have a mechanical shutter.”
Although no one knows for sure what is causing the issue, one reader, eyesee, reckons that the issue could be as simple as a loose or damaged flex connector. “That could explain the green/purple images (some data lines disconnected), or the invalid overtemp warnings (thermistor disconnected).”
The issue (at this point) doesn’t seem to be software related. Force closing the Camera app and resetting the device doesn’t seem to cure the problem for users. On the plus side, it looks as though Apple is taking care of affected customers in a quick and efficient manner. The company is either replacing the defect camera module for customers, or making things easier by swapping out the iPhone 7 Plus for a new one.