Video noise and harsh shadows on green screen caused by feet

Question

We have a recurring shoot where we continue to run into the same two issues. Our set consists of a medical exam table sitting on top of a green screen. The talent sits on the exam table and we record 'Doctor/Patient interviews'.

ISSUE 1: When the talent is on the taller side, their feet hang down past the bottom of the exam table and create really harsh shadows on the green screen, making the footage very difficult to key.

ISSUE 2: The dark area on the front of the exam table, behind the talent's legs, is very noisy.

I believe these two issues are linked and both have to do with lighting. However, I have yet to find a permanent solution to either one of them. I am currently setting a small LED light in front of the camera that helps with the shadows, but it still isn't solving the problem.

Our camera is a Panasonic HMC150 and I use the 'Keylight' effect in After Effects to key the footage. Keying is very difficult around the feet shadows and some of the green reflection shows on the exam table, which in turn, ends up being keyed slightly creating a lot of noise. I use the 'Remove Grain' effect to help remove the noise.

Any advice on a different lighting setup, keying solution, or anything else that could help this situation is greatly appreciated. I've attached images demonstrating the issues.

Answer 1

To reduce or eliminate the greenish reflection on the front of the table, you can buy some dark gray or black construction paper, or something equally non-reflective, cut it to size, and tape it over the 2 dark rectangles on the front of the table.

I have 3 different solutions for the foot-shadows on the floor.

1. You could point a semi-dim spotlight directly on that section of the green screen. Make sure to mask it so it doesn't hit the dark rectangles on the front of the table too much.

2. If the camera is always stationary, you could lower the camera slightly so the talent's feet never extend past the dark rectangle on the front of the table and into the green (as the tip of her left shoe does in the pictures you included). Then you can mask out that part of the shot instead of relying on the Keylight effect.

3. You could just move the camera about a foot closer to the talent so you crop out the bottom of the table (and the green in front of it). You can also do this by cropping the shot during post production.

(Or, obviously, just get shorter talent.)

Answer 2

The best bet is probably a combination of more light and using a flatter exposure. h.264 in particular does very bad with noise levels in shadow as do many CMOS sensors. If you are near the dark end of what the camera can capture, you are going to get lots of noise. The obvious solution is to keep things away from the dark end of what you can capture.

This can be done either by tweaking exposure settings (if the dynamic range of the scene is narrow enough) or by adjusting lighting to be more even. I'd personally go for trying to use a low down and fairly powerful light with a barn door on it to fill the bottom of the table and provide more even lighting underneath as this will also look better in the finished product.

Alternately, as Brett suggested, positioning the actor such that you can mask the area is another option (but would still have a harsh shadow and noise in the dark portions of the video.) Probably best to prevent the dark areas in the first place.

Answer 3

I don't know if this might be an option or even work but, couldn't you get a dark piece of paper or card and create a linear curve from the bottom under the seat to extend to the floor creating a curve just at the end so it looks like part of the chair.