Hello Bernhard,
first of all, I bag pardon for late in the answer...but I did not see before...
For this picture and the other I posted, I follow the suggestion of Rik and Krebs...
I did not think to color before...and now I am working on it to obtain the maximum neutral color possible...
So the tecnic it is the same (oblique illumination), but I change the filter on light and I have introduce some correction in post capture with Photoshop!