Match Lighting a Digital Portrait - Submission

Hey, nice work ddthng ! I think you've totally nailed the exercise. Here are a few notes on each since you mentioned looking for areas to improve. 

Sin City

• The gradient of the light from between his eyes and the rest of his face is much too harsh. In the photo it's a very gradual transition and it's hard to tell exactly where it stops. A spotlight with a large blend size may help. You could also try moving the light closer to his face and letting proximity and the inverse square law do some of that work for you. 
• The folds on his face in the photo are all really defined by shadows. In the render, the laugh lines especially are being washed out. I don't think there's a lot you can do here though, since the faces are just shaped differently and the lines are less defined on the sculpt. 
• Matching the camera angle would also help sell the effect since the composition and lighting are working together here. 

Altered Carbon

• This could also be due to the difference in face shape, but check out how much less light is hitting his left jaw in the photo. Having the light concentrated on his forehead, ear, nose, and just that one sliver of cheek looks really nice. Also try to mimic the triangle shape on his nose. 
• In the photo he's got a pretty strong rim light on his ears that's very slim - just a little sliver. 
• The fact that he's wet is changing the lighting quite a bit, so feel free to crank up the clearcoat on the model's skin material if you want to try and match the reflections. 
• I think the blue light is either multiple lights or very long. Check out how it's not really hitting his chin but is hitting the left side of his upper lip and the under side of his left brow, yet is also hitting the top left of his forehead. 

21 Bridges

• I think the blue light is a bit too saturated, but it also appears to be coming from farther behind him based on the strong rim. 
• The main light from the front appears to be a little more to the left, since his side of his nose all the way to his cheekbone is almost entirely in shadow. 

Agent 47

• Nailed it! The light is hitting his chin a bit more, but it could be a difference in the shape of his face. 

Charles  Xavier 

• In the photo there's a little more emphasis on the upper left rim light than the key light, which you can tell by his nicely shiny head. 

Excellent job! You've obviously got the idea and any one of these could be considered a great setup. Keep up the good work!

Yes! In the skin's Principled shader, set the Subsurface value to something like 0.02 and then enable Subsurface Translucency in the material's settings. 

You can adjust the color of the scattering by changing the R G and B values of the Subsurface Radius.