Depth of Field - Physics Demonstrations - Depth of Field | Physics Undergraduate Labs

If using incandescent or halogen lamps for illumination, allow cooling time before handling and maintain safe distances from metronomes to prevent heat damage or discomfort.

Purpose

Shows how lens aperture controls depth of field — the range of distances that appear in focus simultaneously. Students see the trade-off between light gathering (wide aperture) and depth of field (narrow aperture) using a live camera feed.

Row of Wittner mechanical metronomes on a lab bench shot from low angle; the nearest red-and-white metronome is sharp while background metronomes progressively blur

Same row of Wittner metronomes from the same angle, now with nearly all metronomes in sharp focus from foreground to background

Full setup in lecture hall: camera on tripod between two tables, five metronomes spaced along a meter stick on the far table, desk lamp on the left table providing illumination

Figure 1: Wide aperture (f/2.8): only the nearest metronome is in focus. Background metronomes are progressively blurred.

Figure 2: Narrow aperture (f/16): nearly all metronomes appear in focus simultaneously despite varying distances from the lens.

Figure 3: Complete setup: camera on tripod between lecture tables, metronomes spaced along a meter stick, and desk lamp for illumination. Camera output connects to the AV system.

Safety Warnings

Warning: Lamp Heat Warning

Purpose