The 45-minute tonal study under a single lamp
During a 45-minute timed tonal study, a candidate works on A2 Ingres paper with charcoal and white chalk. The setup is a matte plaster cube, a glazed ceramic cylinder and a folded cotton cloth, lit by a single 60 W bulb placed 1.5 m away at 30° to the left and slightly above the objects. The first lay-in has correct proportions, but the values are compressed: the cube's shadow side is 60% grey, its cast shadow is the same 60%, the cylinder carries a hard white stripe down its centre, and the cloth folds are outlined in black. The candidate has 25 minutes left and wants to clean it up by adding more white highlights. The exam asks for coherent light logic, readable local values and a clear focal area, not photorealistic finish. The paper's tooth is medium; heavy charcoal smudges easily.
1. Identify the two main value-structure errors and explain how they weaken form and light logic.
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The two errors are value compression and misplaced specular. First, the cube's shadow side and cast shadow share the same 60% grey, so the drawing has one dark note instead of a hierarchy. A cast shadow should be darkest at the contact edge and lighter and softer as it travels away, because occlusion and ambient bounce change along its length. If it equals the core shadow, the cube looks pasted onto the paper and the light direction becomes ambiguous. Second, the white stripe down the cylinder's centre treats the highlight as a decorative line rather than a reflection of the source on a curved form. With light from 30° left and above, the terminator runs roughly vertically but shifts with the curvature; the brightest narrow band sits left of centre and slightly above mid-height, surrounded by a half-tone, not a hard white stripe. The black outlines on the cloth also flatten the folds: a dark accent belongs only where a plane turns sharply away or where occlusion occurs, not around every contour.
2. Propose a 25-minute triage: what to erase or rework, what to leave, and how to keep the focal area dominant.
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Triage in order. Lift the black outlines on the cloth with a kneaded eraser and redraw only the three or four folds that describe the main plane changes. Re-state the light family: reserve white chalk for the cube's top plane, the cylinder's specular band and a few cloth crests; bring all shadow sides to a consistent dark, but keep the cube's cast shadow darkest at contact and the cylinder's core shadow distinct from its reflected light. Separate cast from core by adding a thin reflected-light note on the shadow side of the cylinder and cube, using the paper tone or a light chalk touch, not white. Keep the focal area-most likely the cylinder's highlight/terminator and the cloth fold leading to it-at the highest contrast; lose edges at the periphery. Do not add more white globally, because that flattens the range. Work from large planes to small accents and stop with five minutes left for a distance check.
3. If the lamp were moved to a more frontal position, what would change in the drawing and what would remain?
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Frontal light compresses the shadow side, pushes the terminator toward the silhouette and throws the cast shadow behind the objects, so the drawing must rely more on local value and edge quality than on a strong core shadow. The cylinder's specular would broaden and move toward the centre; the cube's top plane would still be lightest, but its front face would gain a subtle gradient. The light logic remains: one source, consistent shadow direction, contact occlusion and reflected light. The mistake would be to keep the old cast-shadow direction or the same high contrast. Instead, reduce shadow-side contrast, preserve a dark accent at contact and use half-tones to keep the form readable.