On-screen composition aids

Two different on-screen composition aids can be activated via the settings panel: composition grids and crop guides. Those are found in Settings > Viewfinder > Overlays.

Composition grids

Light grids that aid during framing and scene compositing. They are very helpful for framing good and aesthetically pleasing photos.

Name	Description
Rule of thirds	The simplest of all grids. Display a grid that subdivides the frame in 3x3 cells. Interesting objects, people and edges should lay in the grid intersections or along edges of the grid.
One quarter	Like the previous one, but the frame is subdivided in 4x4 cells.
Crosshair	A simple grid (2x2 cells), useful to keep horizontal features horizontal, and vertical features vertical.
Triangles	Two types: topleft-bottomright and bottomleft-topright.
Golden spiral	Four directions: top right, bottom right, top left, bottom left.

Crop guides

Allow you to frame objects as if the frame had actually a different aspect ratio as the picture size you have selected. That way, you can use the typical native 4:3 aspect ratio of the sensor to get the maximum output resolution, but frame as if you had, for instance, 3:2 aspect ratio. You can later crop the image to the aspect ratio you used for composition, but if you change your mind, you always have the full resolution shot to keep it or frame (crop) it another way.

Crop guides, when active, show the unused part of the image with a darker semi-transparent overlay. Note that the image is not actually cropped to the selected aspect ratio, crop guides (as the name implies) are just guides for cropping later.

When the composition grids are active, they adapt to the highlighted area left by the selected crop guide.

Guide	Description
Square format	Keeps a centered square on top of the viewfinder, to aid you in framing square shoots.
3:2	That is the typical aspect ratio of DSLRs. Selecting this crop guide, you can frame your shots with 3:2 aspect ratio, while shooting in 4:3. If you really want your photos to come out already with 3:2 aspect ratio, you can select a 3:2 aspect ratio picture size in Settings > General camera settings > Picture resolution.
Widescreen 16:9	Typical aspect ratio of widescreen films. As explained before, if you want to shoot directly in 16:9 format, select a 16:9 aspect ratio picture size in Settings. In that case, no crop guides will be necessary, as the viewfinder will accommodate a 16:9 preview in your device screen (since most devices have 16:9 aspect ratio screens, the typical black bands of surrounding the preview will go away, and the on-screen buttons will show on top of the preview).
Widescreen 16:9 (upper part)	The option Widescreen 16:9 uses the central part of the native shooting resolution to show the guides. You can align the 16:9 crop to the top by selecting this option.
Widescreen 16:9 (lower part)	The same as the previous option, but the crop area is at the bottom of the native frame.
Cinema 2.35:1	This option shows the typical cinematic aspect ratio.
Widescreen multiformat (grid for cinema)	Two crop guides (widescreen 16:9 and cinema 2.35:1) are shown simultaneously. In this option, the grid is adapted to the 2.35:1 area.
Widescreen multiformat (grid for 16:9)	Two crop guides (widescreen 16:9 and cinema 2.35:1) are shown simultaneously. In this option, the grid is adapted to the 16:9 area.