Glasses have subtle effects on light that can be difficult to capture.
The human brain is designed to use icons and symbols to break down and understand the world. When painting, the brain attempts to use those symbols to represent an object rather than what visually makes up the object. An untrained artist will commonly attempt to paint eyeglasses with the symbol for eyeglasses, two circles around the eyes with a line going to each ear. This symbol has little relation to reality and makes a portrait appear childish and unrealistic. Breaking down the object into its basic shapes and displaying the way light interacts with the object will give a more accurate depiction.
Instructions
1. Form the empty spaces around the glasses to use negative space to define the shape. By creating the shape around the glasses and leaving the glasses themselves as an empty space, you force your brain not to attempt to paint a pair of glasses, and therefore use the symbol for glasses, but to instead just create the shapes it is seeing. After the negative space has been captured, the pure shape of the glasses is defined.
2. Note any magnification that may occur from the lenses. Some glasses may make the wearer's eyes appear slightly larger, or offset the eye slightly from the rest of the face when viewed from a three-fourths angle. This is a subtle effect and you must take care not to overplay it, as it will make your painting appear unreal or cartoonish if overdone.
3. Preserve any highlights on the lenses. The light reflecting off the surface of the lens may create a bright spot. Take care to start from lighter shades and deepen the darker areas as you go, to make sure the highlights stay intact.
4. Darken any shadows cast by the glasses. The glasses are a three-dimensional object set apart from the wearer's face. Light sources will cast some form of shadow on the wearer, and capturing those shadows will give the portrait a more realistic and deeper look.
