Question: Can anyone refer me the Phong reflection model parameters for a face image taken for web-cam?

Details:

I am doing 3D reconstruction of 2D images using 3D Morphable Model as in this paper Vetter & Blanz, 2003.

There is a cost function which needs to be optimized using Newton Method. I need to give initialization values for the Newton method.

The below equation is the phong reflection model of an image. The ambient, diffuse and the specualr components are shown.

Phong Reflection Model wiki

Phong Parameters: Ks, Kd, Ka, α, Lm, V

I am estimating the above parameters using Newton method. The image is of human face and the camera is web-cam.

I gave the below values: Ks = Kd = Ka = 0.6 α = 5 Lm = [0 1 1] V = [0 0 1]

Can anyone comment on the above values and what can be a good initialization values for the parameters??