In After Effects, changing the "ratio" of a project typically refers to modifying the aspect ratio of your composition. This is done by adjusting the composition's dimensions (Width and Height) and potentially its Pixel Aspect Ratio.
Understanding Composition Settings
The core of your After Effects project is the composition. Its settings define the frame size and aspect ratio.
- To access composition settings, select the composition in the Project panel or timeline, then go to Composition > Composition Settings (or press Ctrl+K on Windows / Cmd+K on Mac).
Within the Composition Settings window, the key parameters for changing the ratio are:
Basic Settings
- Width: The horizontal dimension of your composition in pixels.
- Height: The vertical dimension of your composition in pixels.
- Pixel Aspect Ratio: Defines the shape of individual pixels. For most digital video formats (like HD, 4K, web video), this should be set to Square Pixels (1.0). Non-square pixels (like DVCPRO HD or Anamorphic) mean the display ratio differs from the pixel dimensions ratio.
The aspect ratio you see is the ratio of Width to Height (assuming Square Pixels). For example, 1920x1080 pixels gives a 16:9 aspect ratio.
Steps to Change Composition Ratio
Here's how to modify your composition's dimensions and aspect ratio:
- Open the Composition Settings window for the desired composition (Composition > Composition Settings or Ctrl+K/Cmd+K).
- Under Basic Settings, locate the Width and Height fields.
- Manually type in the desired new dimensions. For example, to change from HD (1920x1080) to a wider cinematic ratio, you might enter 1920x810 (which is a 2.37:1 ratio, similar to cinemascope). Or, as seen in the reference, to change to a 4K width, you could type 3840 in the Width field and adjust the height accordingly for your target aspect ratio (e.g., 2160 for 4K UHD 16:9).
- Ensure the Pixel Aspect Ratio is set correctly, usually Square Pixels.
- If you have existing layers in the composition, changing the dimensions will change the frame size they appear within. You may need to resize or reposition these layers to fit the new frame.
- The reference mentions clicking "scale" after typing the new width (like 3840). This indicates that After Effects provides options (often found near dimension changes or when using script/extension tools like Composition Profiler or scripts from Ae scripts + plugins) to automatically scale existing layers within the composition to fit the new dimensions. This can be a significant time-saver. Look for options like "Scale content" or similar features when resizing.
- Click OK to apply the new settings.
Resizing Existing Layers
After changing composition dimensions, your existing layers (footage, solids, text, etc.) will retain their original size relative to the old composition size.
- Manual Adjustment: Select layers and adjust their Scale and Position properties in the timeline or using the Selection tool in the Composition panel.
- Automatic Scaling (as hinted by reference): Some tools or built-in features might offer to scale layers automatically when the composition size changes. If a "scale" option is available after changing dimensions, clicking it can help fit your existing content into the new frame.
Common Aspect Ratios & Resolutions
Here's a quick look at common aspect ratios and their corresponding resolutions with Square Pixels:
| Aspect Ratio | Description | Common Resolutions (Width x Height) |
|---|---|---|
| 16:9 | Widescreen (HD, UHD) | 1280x720, 1920x1080, 3840x2160 |
| 4:3 | Standard Definition (older) | 640x480, 720x534, 800x600 |
| 1:1 | Square | 1080x1080, 1920x1920 |
| 9:16 | Vertical (Mobile) | 1080x1920, 2160x3840 |
| 2.35:1 / 2.39:1 | Cinematic Widescreen | 1920x817, 2048x858, 3840x1634 |
By changing the Width and Height in your composition settings to match one of these ratios (or a custom one), you change the ratio of your After Effects project.
