Q: Rear camera not working after iOS8.4 update

Hello there, Crimson88.

It sounds like you've done some great troubleshooting already for the issue you are seeing with your rear facing camera and flash. The following Knowledge Base article offers some great recommendations review as well:

Get help with the camera on your iPhone, iPad, or iPod touch - Apple Support

You see a closed lens or black screen

If you see a closed lens or black screen when you open the Camera app, try these steps:

1. Make sure that there’s nothing blocking the camera lens. If you’re using a case, try removing it.
2. Force the app to close, then open the Camera app again.
3. Restart your device, then open the Camera app again.
4. If your device has a front and rear camera, try both cameras by tapping  (camera swap icon). If you see the closed lens or black screen on only one camera, take your device to an Apple Retail Store or Authorized Service Provider for more help.

There are also some steps for resolving flash issues as well:

Your flash isn't working

If the flash isn’t working, or if it’s going off every time you take a photo, check your flash settings. Tap the lightning bolt in the upper left of the screen to choose a different setting.

If you take extended video with the flash on, or you’re using the device in a very warm environment, you might see  (disabled flash icon). You won’t be able to use the flash until your device cools down.

If the flash is on when you’re not using the camera, check the Control Center to see if the flashlight is on.

Thanks for reaching out to Apple Support Communities.

Cheers.