This is the continuation of Great Drawing Tutorial Collection by EclecticAsylum - Part II. If you follow the videos from the beginning of this tutorial video collection, you will understand about the math and science of drawing portraits. Jason will tell you about Sketching and Value Shapes in the following videos.
Learn to Draw Portraits - Ep.4B Sketching
Learn to Draw Portraits - Ep.5A Value Shapes
Learn to Draw Portraits - Ep.5B Value Shapes
I will continue adding the other parts tomorrow... so, stay tune!
update: I have to remove and split the tutorial to 3 videos per post due to limitation of some browser which cannot load all the videos. Sorry for the inconvenient. Just stay tune and you'll get all videos here