Open Camera is a fully featured and completely free Camera app for Android phones and tablets.

Features:

• Option to auto-stabilize so your pictures are perfectly level no matter what (see example image).
• Expose your camera's functionality: support for focus modes, scene modes, color effects, white balance, ISO, exposure compensation/lock, face detection, torch.
• Video recording (including HD).
• Handy remote controls: timer (with optional voice countdown), auto-repeat mode (with configurable delay).
• Option to take photo remotely by making a noise (e.g., voice, whistle), or by voice command "cheese".
• Configurable volume keys.
• Optimise GUI for left or right-handed users.
• Zoom via multi-touch gesture and single-touch control.
• Option to lock orientation to portrait or landscape for photo or video. Upside-down preview option for use with attachable lenses.
• Choice of save folder (including support for Storage Access Framework).
• Disable shutter sound.
• Overlay a choice of grids and crop guides.
• Optional GPS location tagging (geotagging) of photos and videos; for photos this includes compass direction (GPSImgDirection, GPSImgDirectionRef).
• Apply date and timestamp, location coordinates, and custom text to photos; store date/time and location as video subtitles (.SRT).
• Yes you can take a selfie (also known as front camera), includes support for "screen flash".
• Support for (some) external microphones.
• Widget to automatically take a photo after launching.
• Support for Camera2 API: manual focus distance; manual ISO; manual exposure time; RAW (DNG) files.
• Support for HDR and Exposure Bracketing (Camera2 only).
• Dynamic range optimisation mode.
• Small file size.
• Completely free, and no ads in the app (I only run ads on the website). Open Source.

(Some features may not be available on all devices, as they may depend on hardware or camera features, the Android version, etc.)