what size hole for pinhole camera
Pinhole cameras rely on a precisely sized hole to project sharp images without a lens, balancing sharpness against diffraction blur. The ideal hole size depends on your camera's focal length (distance from hole to film/sensor).
Optimal Formula
Use this standard equation for the best diameter ddd in mm:
d=1.9fd=1.9\sqrt{f}d=1.9f
where fff is focal length in mm.
This comes from Lord Rayleigh's research, refined over decades, optimizing for visible light around 550 nm wavelength.
Size Chart by Focal Length
Here's a practical table of recommended diameters (in mm and inches) from tested charts—round your pinhole to the nearest drill bit or laser-cut size.
| Focal Length | Diameter (mm) | Diameter (inches) | f-stop (approx) |
|---|---|---|---|
| 25 mm (1") | 0.12 | 1/210 | f/208 |
| 50 mm (2") | 0.17 | 1/150 | f/294 |
| 75 mm (3") | 0.21 | 1/120 | f/357 |
| 100 mm (4") | 0.24 | 1/106 | f/417 |
| 150 mm (6") | 0.29 | 1/87 | f/517 |
Making Your Hole
- Material : Thin brass or aluminum foil (0.02-0.05 mm thick) for minimal distortion—no paper or plastic.
- Tools : Needle, pin, or laser cutter; sand edges smooth to avoid burrs.
- Test it : Measure with a microscope or caliper; too big = blur, too small = diffraction haze.
General range for DIY: 0.2-1.0 mm works for most hobby cams.
Common Pitfalls & Tips
Too large a hole (e.g., 1.5 mm on 50 mm focal) causes fuzzy edges like a wide lens gone wrong; too tiny darkens shots.
Experiment: Start with the formula, then tweak ±10% based on your light—sunny days forgive slight errors. Forums buzz with 2025 trends like smartphone pinhole hacks using 0.3 mm holes for 40 mm "focals."
TL;DR : Measure focal length, plug into d=1.9fd=1.9\sqrt{f}d=1.9f, aim 0.15-0.3 mm for typical setups.
Information gathered from public forums or data available on the internet and portrayed here.
