Hello kaylea165,
Thank you for posting to Apple Support Communities.
If the preview is black when attempting to take a photo, this usually isn't caused by heat. If you're experiencing this issue with both the front and back cameras, it's possible there is something hardware related happening. We do have some steps that may help resolve this. Here's how to complete them:
1. Remove any case, accessory, or film that might block the camera or that places a magnet near the camera.
2. Test the camera by trying to take a photo.
3. If the photo is blurry, clean the front and back camera lenses with a microfiber cloth. If you see dirt or debris inside the lens or if the camera lens appears to be misaligned or blocked, contact Apple Support for help with your iPhone, iPad, or iPod touch.
4. Restart your iPhone, iPad, or iPod touch.
5. Test the camera again by taking a photo. If your device has a front and rear camera, check if one or both isn’t working. To switch cameras, tap the rotate button
.
This information is provided in If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support.
If that doesn't resolve the issue, contact Apple Support for service options.
Take care.