diff --git a/SETUP.md b/SETUP.md
index deae0a3..cba3c00 100644
--- a/SETUP.md
+++ b/SETUP.md
@@ -79,8 +79,9 @@ This contacts the `mtredisalize` server running at localhost port 6379 to fetch
 need a `colors.txt` to map the block nodes to pixel colors of your map. The repository contains
 [one](https://bitbucket.org/s_l_teichmann/mtsatellite/raw/default/colors.txt).  
 If you want to have certain nodes to be transparent you can add `-transparent=true` to the
-options. In this case if the colors from colors.txt do have a forth color component with a numerical
-value lower than 255 (e.g 128) the corresponding pixels on the resultung tiles would be transparent.  
+options. In this case if a color from colors.txt does have a forth color component the numerical
+value between 0 (fully transparent) and 255 (fully opaque) will be the base transparency of the
+pixel. Every depth meter of the same material will reduce the transparency by 2%.  
 See `mtseeder --help` for all options. 
 
 The `-workers=` option and the `GOMAXPROCS=` environment variable are completely optional but very useful
diff --git a/common/colors.go b/common/colors.go
index 83044bf..e27f489 100644
--- a/common/colors.go
+++ b/common/colors.go
@@ -113,11 +113,13 @@ func (colors *Colors) BlendColors(span *Span, col color.RGBA, pos int32) color.R
 	if curr == nil {
 		return col
 	}
-	const scale = float32(1) / float32(100)
+	const scale = float32(1) / 100
 	for ; curr != nil; curr = curr.Next {
-		// At least 50% attenuation + 2% extra for each depth meter.
-		factor := float32(min(100, 50+(curr.To-curr.From)*2)) * scale
-		col = BlendColor(colors.Colors[curr.Value], col, factor)
+		c := colors.Colors[curr.Value]
+		// At least alpha channel attenuation + 2% extra for each depth meter.
+		base := (int32(c.A) * 100) / 255
+		factor := float32(min(100, base+(curr.To-curr.From)*2)) * scale
+		col = BlendColor(c, col, factor)
 	}
 	return col
 }