Fig. 7-1A. Four still-life objects are illuminated with ideal light coming from the right side and toward the front of the table.  Form is always fullest and most classic under  side.front lighting

 

Fig. 7-1B.The same four objects now receive full light from a lamp placed directly in front of them.   Front lighting tends to flatten out forms because it floods the objects with light, causes middle tone to crowd their edges, and virtually eliminates form dark.

Fig. 7-1C. Top lighting is difficult to arrange over still lifes, but it can be attractive and a welcome change from side/front.

 

Fig. 7-1D. Back lighting is the most dramatic, providing you are willing to lower the key of your painting and play up the contrast of extremes of silhouettes and halo-like edges of form.