Unauthorized Access Exception when trying to write to internal storage.

I'm trying to save a screen capture from an application I'm building. ScreenCapture works great but it saves to persistent path and I want to put the screenshots in the camera folder. But trying to save the files there, moving them there or even just creating a new folder in internal storage returns the same result: "UnauthorizedAccessException: Access to the path "/sdcard/DCIM" is denied" (replace directory for wherever I'm trying to access). My player settings are set to write permission internal but it doesn't seem to help.