i was on the search ,for a good and simple index of refraction equation,that can calculate complex IOR with n and k extinction values,and that i can use for the thin film shader.i found some usefull equation ,that i was testing as stand alone conductor shader,to see if its accurate enough ,for the thin film shader implementation in cycles.

first testrender with gold values from the refractive index website.i used the 0.6 for red, 0.56 for green and 0.45 um for blue on the website and put the given n and k values into the shader.here the result.

edit,the equation seems to do the work.i am not sure about the accuracy.if someone knows some reference renderings with n k datas for comparison,a link would be helpfull.

btw the hdri looks a bit yellowish,this was used in the thinfilm paper renders.

edit,silver

copper