01-12-2014, 09:32 AM
Nice studies! I'll attempt to answer your question, though this is only what I have deduced through my studies. I believe it is a core shadow, the reason for this is because core shadows only appear when the surface is perpendicular to the light source. On the two examples you pointed out, both go into definite shadow, the one of the side of the head is the best example of this since it has less reflected light. The one in the ear, the only reason it is not as dark as the plane facing away on the back of the head is for this reason, the reflected light, which is actually fairly strong.
As for the ones without a core shadow, this is the part I am not 100% sure on and would love someone to confirm it, is that the side of the head isnt actually in shadow, its the half tone. Because that plane of the head and the planes aroudn the lips, are still (JUST) facing towards the light source, the reason they are darker is because of the obtuse angle they are when compared the the light source, so while they are darker than those in direct like, they aren't yet the shadow side of the face..
Incase that doesnt make sense I did a quick drawing.
There are three sections I am talking about. (Sorry they are backwards..
C: Receives a 1:1 ratio of light, where is the width of the plane receives the same width of light rays.
B: Because it is turned slightly, receives a 1:1.2 maybe ratio of light, so for the same amount of light as plane C, it has to be spread over 1.2 times the space.
A: Because it is turned a lot, but still facing forward, it receives a ratio of 1:2, maybe even 1:3. So for the same amount of light as Plan C, it has to cover two or three times the area.
This then means that A isnt actually in shadow, but is still one of the light planes of the face, even though when compared to B and C it looks like it is.
Where as from the top view, D, is your shadow side since it is facing away from the light and between D and C is where the core shadow will be.
That was a really long explanation and I have no idea whether it even answered the question >.>
As for the ones without a core shadow, this is the part I am not 100% sure on and would love someone to confirm it, is that the side of the head isnt actually in shadow, its the half tone. Because that plane of the head and the planes aroudn the lips, are still (JUST) facing towards the light source, the reason they are darker is because of the obtuse angle they are when compared the the light source, so while they are darker than those in direct like, they aren't yet the shadow side of the face..
Incase that doesnt make sense I did a quick drawing.
There are three sections I am talking about. (Sorry they are backwards..
C: Receives a 1:1 ratio of light, where is the width of the plane receives the same width of light rays.
B: Because it is turned slightly, receives a 1:1.2 maybe ratio of light, so for the same amount of light as plane C, it has to be spread over 1.2 times the space.
A: Because it is turned a lot, but still facing forward, it receives a ratio of 1:2, maybe even 1:3. So for the same amount of light as Plan C, it has to cover two or three times the area.
This then means that A isnt actually in shadow, but is still one of the light planes of the face, even though when compared to B and C it looks like it is.
Where as from the top view, D, is your shadow side since it is facing away from the light and between D and C is where the core shadow will be.
That was a really long explanation and I have no idea whether it even answered the question >.>