Drawing faces in these points of view is extremely difficult because of the foreshortening that takes place as the head is rotated and presented from a more dynamic perspective.

All the proportions we’ve learned in the eye level front, side, and three quarter views of the female head to help us place the facial features become skewed. Their proportional relationships in terms of scale and placement are all adjusted to convey the depth and dimensions of the head as it protrudes and recedes in the upward and downward, three quarter representations of the head.

Not only that, but the shape of the head’s structure and the facial features themselves are also affected, causing us additional confusion as to how the eyes, nose, mouth and ears should be drawn from one view point to the next. This ultimately means that there’s no one way to draw the features, and that in reality they have an endless amount of variations that each correlate with whatever angle the head is being drawn on.

As mentioned previously, the structure of the head and its shape also becomes skewed when looking at the head on a top down or bottom up, three quarter angle. This is most noticeable around the jaw line and brow, but also applies to the entire face as a whole in more subtle ways.

More info - https://skl.sh/2ZM6vK2