This is a detail of " The Landing of Marie DeMedici at Marseilles" by Peter Rubens. This painting in the Louvre is part of a group of enormous paintings called the Marie De Medici cycle. The paintings in this room left me awestruck. Here we are looking at the back of one of the nyriads in the lower left hand corner of the painting ( displayed in yesterdays post) This is a text book example of how to obtain form.
The halftones are actually keyed pretty low, compare her to the girl to the left who is painted up in a much higher key. Impressionists who work in a very high key often have difficulty expressing form and dissolve it in light. Artists very concerned with form often paint in a lowered key, think Rembrandt. Having this key a little lowered is an advantage in that you have plenty of room to place the highlight well above its value. Imagine a guitarist playing with his amp turned up to 10 ( or 11 in the case of Spinal Tap ) . When the time comes to take his solo he reaches back to turn up his amp, and he can't. Its already all the way up. If you are playing at the top of your value range, or at the bottom you cant place an accent above or below. You have left yourself no room. So be careful and leave yourself some room to move. This is one of the big secrets to painting snow.
The entire figure is enclosed in a bulging writhing line, notice the line showing the lower part of the ribcage on the left lower driving in and over the form of the hip below. The line of the deltoid or upper shoulder enters the outline to overlap the form of the bicep below it.
There is no doubt at all what is in shadow and what is not, look at the bedbug line, Rubens has "jumped the light" too. He has put all the shadow well over to the left. That gets most of the figure out into the light. He has downplayed the cast shadow across the upper part of the right arm, he has that huge beam throwing a tiny shadow, just enough to show us the squareness that he is using there to describe the arm. More tomorrow.