iPhone 5 camera stopped working after update to iOS 8.

Hello there, iAachen.

The following Knowledge Base article offers up some great information on troubleshooting the issue you're describing:

iPhone: Hardware troubleshooting

http://support.apple.com/kb/TS2802

Particularly:

Camera isn't functioning or has undesired image quality

1. If the screen shows a closed lens or black image, force quit the Camera app.
2. If you do not see the Camera app on the Home screen, try searching for it in Spotlight. If the camera does not show up in the search, check to make sure that Restrictions are not turned on by tappingSettings > General > Restrictions.
3. Ensure the camera lens is clean and free from any obstructions. Use a microfiber polishing cloth to clean the lens.
4. Cases can interfere with the camera and the flash. Try gently cleaning the lens with a clean dry cloth or removing the case if you see image or color-quality issues with photos.
5. Try turning iPhone off and then back on.
6. Tap to focus the camera on the subject. The image may pulse or briefly go in and out of focus as it adjusts.
7. Try to remain steady while focusing:
   • Still images: Remain steady while taking the picture. If you move too far in any direction, the camera automatically refocuses to the center.
     Note: If you take a picture with iPhone turned sideways, it is automatically saved in landscape orientation.
   • Video: Adjust focus before you begin recording. You can also tap to readjust focus while recording. Exiting the Camera application while recording will stop recording and will save the video to the Camera Roll.
     Note: Video-recording features are not available on original iPhone or iPhone 3G.
8. If your iPhone has a front and rear camera, try switching between them to verify if the issue persists on both.

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro.