How to fit the parameters precisely

[yfji]

Hi juyong! I read your paper and wrote a small script to fit id and expression parameters. However I have several questions.
1.In equation 5, if I fit only using landmark term, I can fit at most 40-d id param and 10-d exp param. If longer, the algorithm does not converge.
2.Does the photo consistency term help for the precision of id param and exp param? Or they are only used for the albedo param.
3.How to use Gauss Newton to minimize a function with form like: f(x)=1/MSigma(||g(x)||^2)+1/NSigma(||h(x)||^2)?
Thank you very much!