Sup man, those studies look great! I do have a piece of feedback regarding spheres and ellipses. When doing those ellipses inside the circles, do pay attention to the distance of both sides of the ellipse to the edge. Since the circle is perfectly symmetrical those distance must match.
Also the ellipse on a perfect circle never meet the edge on a straight angle (excluding when it's seen straight on), they do so in a soft circular way, to represent the volume of the sphere.
Did a little example to illustrate what i mean.
I do like the way you present to the viewer those studies, they look very organised and clean. Keep it up!
