How to Use Blender Defocus Node for Depth of Field

Using the Defocus node in Blender's Compositor allows you to apply realistic depth of field (DoF) effects during post-processing instead of calculating it in-camera. This guide covers how to enable the required depth pass, connect the Defocus node in the Compositor workspace, and fine-tune blur and bokeh settings to achieve clean, cinematic background and foreground separation without increasing 3D render times.

Step 1: Enable the Z (Depth) Pass

Before rendering, you must tell Blender to output depth information alongside the image:

  1. Open the View Layer Properties tab (the icon resembling stacked layers in the Properties panel).
  2. Expand the Passes section and go to Data.
  3. Check the box for Z (also known as the Depth pass).
  4. Render your image or animation frame (press F12).

Step 2: Set Up the Compositor

  1. Switch to the Compositing workspace at the top of the Blender interface.
  2. Check the Use Nodes checkbox at the top toolbar.
  3. You will see a Render Layers node connected to a Composite node.
  4. Press Shift + A, search for Defocus, and place the node between the Render Layers and Composite nodes.
  5. Press Shift + A, search for Viewer, and connect the Defocus node's Image output to the Viewer node to see real-time updates in the background (press V to zoom out the backdrop, Alt + V to zoom in).

Step 3: Connect the Node Inputs

Link the outputs from the Render Layers node to the Defocus node:

  • Connect Render Layers (Image) to Defocus (Image).
  • Connect Render Layers (Z) to Defocus (Z).
  • Connect Defocus (Image) to both the Composite and Viewer nodes.

Step 4: Configure Node Parameters

Adjust the following key settings inside the Defocus node:

  • Use Z-Buffer: Check this option to instruct the node to use the depth pass connected to the Z input.
  • Z-Scale: Leave this at 0.000 to automatically read the camera's focus distance set in the 3D scene. If you uncheck "Use Z-Buffer", you can manually control the focal distance using this value.
  • f-Stop: Controls the depth of field aperture size. Lower values (e.g., 1.4 to 2.8) produce a shallow depth of field with heavy blur, while higher values (e.g., 8.0 to 16.0) keep more of the scene sharp.
  • Max Blur: Limits the maximum pixel radius of the blur. Setting this too high can cause artifacting, while setting a cap (e.g., 16 to 32 pixels) maintains smooth performance and avoids fringing.
  • Threshold: Helps eliminate aliasing artifacts along high-contrast depth edges. Adjust this slightly if you see sharp outlines around blurred objects.
  • Bokeh Type: Choose the shape of out-of-focus highlights (e.g., Octagonal, Hexagonal, Circular) to match real-world camera lens characteristics.

Step 5: Adjust Focus Distance

To change what is in focus:

  1. Select your Camera in the 3D viewport or Outliner.
  2. Go to the Camera Properties tab.
  3. Expand Depth of Field and set your Focus Object or adjust the Focus Distance metric manually.
  4. The Defocus node in the Compositor will automatically update the in-focus area according to these camera settings.