diff --git a/docs/src/content/docs/api-channel.md b/docs/src/content/docs/api-channel.md
index 29808348..fb8ed333 100644
--- a/docs/src/content/docs/api-channel.md
+++ b/docs/src/content/docs/api-channel.md
@@ -61,6 +61,8 @@ const rgba = await sharp(rgb)
 
 Extract a single channel from a multi-channel image.
 
+The output colourspace will be either `b-w` (8-bit) or `grey16` (16-bit).
+
 
 **Throws**:
 
diff --git a/lib/channel.js b/lib/channel.js
index 46bce3d5..b6381ae9 100644
--- a/lib/channel.js
+++ b/lib/channel.js
@@ -74,6 +74,8 @@ function ensureAlpha (alpha) {
 /**
  * Extract a single channel from a multi-channel image.
  *
+ * The output colourspace will be either `b-w` (8-bit) or `grey16` (16-bit).
+ *
  * @example
  * // green.jpg is a greyscale image containing the green channel of the input
  * await sharp(input)