add luma video review explanation

README.md

@@ -268,6 +268,11 @@ Previously we had calculated that we needed [278GB of storage to keep a video fi
 >
 > ![ycbcr color histogram](/i/yuv_histogram.png "ycbcr color histogram")
 
+### Color, luma, luminance, gama video review
+
+Watch this incredible video explaining what is luma and learn about luminance, gamma, and color.
+[![Analog Luma - A history and explanation of video](http://img.youtube.com/vi/Ymt47wXUDEU/0.jpg)](http://www.youtube.com/watch?v=Ymt47wXUDEU)
+
 ## Frame types
 
 Now we can move on and try to eliminate the **redundancy in time** but before that let's establish some basic terminology. Suppose we have a movie with 30fps, here are its first 4 frames.