diff --git a/README.md b/README.md
index e8c13ac..acda426 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,41 @@ compressed encoding, `width` and `height` are the image's dimensions, not the le
 |---|---|
 | `tick` | Publishes one frame. Wire to `dora/timer/millis/N`; the node stops when it closes. |
 
+## Configuring it
+
+Every setting below is an environment variable, which is convenient for one and
+awkward for several. A dataflow can carry them instead, per node, which keeps the
+configuration with the wiring it belongs to and out of whatever shell happens to start
+it:
+
+```yaml
+nodes:
+  - id: camera
+    git: ssh://git@gitea.liria.cl:5001/liria/dora-webcam.git
+    tag: v0.1.0
+    build: uv pip install .
+    path: dora-webcam
+    env:
+      CAMERA_ID: usb-Acme_Webcam
+      IMAGE_WIDTH: 1280
+      IMAGE_HEIGHT: 720
+      ENCODING: jpeg
+      JPEG_QUALITY: 85
+      FLIP: HORIZONTAL
+    inputs:
+      tick: dora/timer/millis/33
+    outputs:
+      - image
+```
+
+Values may be strings, numbers or booleans, and dora applies them to both the build and
+the run.
+
+**A node's `env:` wins over the environment the dataflow was started in.** A variable
+the node does not set still passes through, so `PREVIEW=true dora run ...` works
+alongside the block above — but a variable pinned there cannot be overridden from the
+shell, which is worth remembering before pinning something a test needs to vary.
+
 ## Environment variables
 
 | Variable | Default | Meaning |
diff --git a/dataflow.yml b/dataflow.yml
index bd947cd..4be4fac 100644
--- a/dataflow.yml
+++ b/dataflow.yml
@@ -7,6 +7,16 @@ nodes:
   - id: camera
     path: dora-webcam
     build: uv pip install .
+    # Settings belong here rather than in the environment of whatever starts the
+    # dataflow. Deliberately empty: a node's `env:` wins over the shell, and CI
+    # passes CAPTURE_FRAMES in through the shell, so pinning one here would
+    # silently override it. See the README for a populated example.
+    #
+    # env:
+    #   CAMERA_ID: usb-Acme_Webcam
+    #   IMAGE_WIDTH: 1280
+    #   IMAGE_HEIGHT: 720
+    #   ENCODING: jpeg
     inputs:
       tick: dora/timer/millis/33
     outputs: