Line, value, chiaroscuro and tonal modelling
Here the exam tests whether you can control the graphic means themselves: what a line is doing, and whether a value structure explains a light source. A technically tidy drawing with a collapsed value range loses marks against a rougher one with clear light logic, a full scale and controlled edges.
Line as a decision
- Contour describes the outer limit; interior line describes plane breaks and structure. Line weight (pressure, sharpening, speed) carries emphasis: heavier at contact points and shadow side, lighter where the form turns away.
- Hatching (rayado), cross-hatching and directional strokes are value tools; their spacing and pressure matter more than their number.
Value logic
- Use a 0–10 scale and identify your darkest dark and lightest light early.
- Five zones on any lit form: highlight, half-tone, core shadow (sombra propia), reflected light, cast shadow (sombra arrojada), plus an occlusion dark where forms touch. The terminator separates light from shadow and follows the form's geometry - on a sphere it is a great circle perpendicular to the light direction.
- Illumination falls off with the angle of incidence and with distance, so cast shadows are darkest and sharpest at contact and soften outward.
Historical vocabulary
- Chiaroscuro as modelling through light and dark; tenebrism as extreme dark ground with a narrow lit passage (Caravaggio, Rembrandt, and the Spanish tradition of Ribera and Zurbarán).
Worked example
A sphere lit from upper left. Place the terminator as a circle tilted away from the light; put the core shadow just inside the shadow side, then a narrow reflected-light band below it, sourced from the table. The darkest note is the occlusion under the sphere, not the core shadow. The cast shadow is darkest at contact and lightens as it travels right. Build with stepped values (three or four), not continuous smudge, so the steps can be checked.
Traps that cost marks
- A dark outline around the whole form (halo), which flattens it.
- Reflected light drawn as bright as the highlight.
- A uniformly dark cast shadow with no contact dark.
- Using black for shadow in graphite instead of pushing value.
- Smudging everything, so no edge is crisp and the drawing loses structure.