diff --git a/include/led-matrix.h b/include/led-matrix.h
index 637b98033..8b853678c 100644
--- a/include/led-matrix.h
+++ b/include/led-matrix.h
@@ -85,6 +85,8 @@ class RGBMatrix : public Canvas {
   void set_luminance_correct(bool on);
   bool luminance_correct() const;
 
+  // Set brightness in percent. 1%..100%.
+  // This will only affect newly set pixels.
   void SetBrightness(uint8_t brightness);
   uint8_t brightness();
 
diff --git a/lib/framebuffer-internal.h b/lib/framebuffer-internal.h
index 0b77d79ab..7937b611c 100644
--- a/lib/framebuffer-internal.h
+++ b/lib/framebuffer-internal.h
@@ -43,7 +43,11 @@ class Framebuffer {
   void set_luminance_correct(bool on) { do_luminance_correct_ = on; }
   bool luminance_correct() const { return do_luminance_correct_; }
 
-  void SetBrightness(uint8_t brightness) {  brightness_ = brightness; }
+  // Set brightness in percent; range=1..100
+  // This will only affect newly set pixels.
+  void SetBrightness(uint8_t b) {
+    brightness_ = (b <= 100 ? (b != 0 ? b : 1) : 100);
+  }
   uint8_t brightness() { return brightness_; }
 
   void DumpToMatrix(GPIO *io);
diff --git a/lib/framebuffer.cc b/lib/framebuffer.cc
index 6f20966d0..5eabeabb1 100644
--- a/lib/framebuffer.cc
+++ b/lib/framebuffer.cc
@@ -162,7 +162,7 @@ inline uint16_t Framebuffer::MapColor(uint8_t c) {
 
   if (do_luminance_correct_) {
     static uint16_t *luminance_lookup = CreateLuminanceCIE1931LookupTable();
-    return COLOR_OUT_BITS(luminance_lookup[c * 100 + brightness_ - 1]);
+    return COLOR_OUT_BITS(luminance_lookup[c * 100 + (brightness_ - 1)]);
   } else {
     // simple scale down the color value
     c = c * brightness_ / 100;