Hello wrentie,
Thank you for participating in the Apple Support Communities! We understand that your Screen Time report is showing unexpected usage for the Camera app on your iPhone. Your privacy is important and you've come to the right place for help.
To help further isolate potential causes, we'd like to start by having you take a look at the battery usage for your iPhone following the steps in the resource below. Specifically, what does background activity look like for the Camera app and does the usage match what you're seeing in Screen Time? Do you see background activity for any other apps that use the Camera on your iPhone?
About the battery usage on your iPhone, iPad, and iPod touch - Apple Support
If you're seeing a high amount of background activity for camera apps, this could indicate that the app didn't properly close, continuing to run in the background even while your display was locked. In that scenario, try testing if the issue still persists after forcing the app to close:
How to force an app to close on your iPhone, iPad, or iPod touch
Let us know what you find.
Take care.
