Check out some of our helpful tips regarding light source that we teach in our course, The Practice of Botanical Drawing!
Ideal Light Source Setup
Light should hit your subject at about a 45 degree angle from the upper left. Use a box to block out other light sources in the room. Notice where shadows and highlights appear. The cast shadow should appear on the lower right of the subject.
Basic geometric shapes with correct lighting
Use these shapes as “light source models” for rendering botanical subjects with correct light source. Reference a cylinder for a branch or a stem, a sphere for a tomato, a cone or a cup for a flower, and two planes for a leaf.
Setting up a model and lighting it correctly can be a great reference tool. If you don’t have basic 3D shapes on hand, try using household objects such as pencils or chopsticks, etc.
Cross-contour lines can help with understanding three-dimensional surfaces, how they bend away from and toward the light, and how to shade correctly. Cross-contour lines are also useful when applying pattern to three-dimensional form.
Highlights on shiny surfaces will appear much brighter than on dull surfaces. In order to create the illusion of three dimensions on paper, show a highlight in the proper place, whether you “see” it or not. Highlights should not appear as a hole or empty space. Highlights should shimmer!
Cast shadows are powerful, but remember they are supporting actors, not the stars of the show. A shadow should not feel solid; it is a subtle reminder that a subject is sitting on a flat surface. Cast shadows start darkest at the base of the subject and fade lighter as they move away from the subject. They should always follow the curves of the subject to emphasize its shapes.
Note: When a cylinder crosses over a perpendicular cylinder, both sides of the bottom cylinder will not have a cast shadow. Only the side furthest from the light source would have a cast shadow.
A reflective highlight is light bouncing off a surface and back onto a subject at the bottom of the shadow side or next to an overlapping area. It is very subtle and is not always necessary. It can show contrast between the subject, the cast shadow, and the surface it is sitting on. Keep the reflective highlight slightly darker than the highlight. If the highlight is value 1, the reflective highlight should be about value 5. Reflective highlights work best when they are irregular and sort of glowing and do not have a straight edge. Like a highlight, a reflective highlight should be irregular and diffused. If your reflective highlight is too white, add a little color to tone it down.