Alargar abertura pinhole é **degradação controlada** — troca resolução por velocidade e mood. Aqui está breakdown quantitativo.
| Parâmetro | Mudança | Resultado Visual |
|---|
| Throughput luz | ∝ d² | 4× brighter per 2× diameter. Exposição cai minutos para segundos. |
| Geometric blur circle | = d | Point source becomes disk diameter d. Sharpness ∝ 1/d. |
| Diffraction blur (Airy) | ∝ 1/d | Actually *improves* with larger hole, but geometric blur dominates past d_opt. |
| Total blur (RMS) | √(d²/12 + (1.22λf/d)²) | Minimum at d_opt ≈ 1.9√(fλ). Larger = worse. |
| Depth of field | Effectively ∞ at d_opt; shrinks as d ↑ | Large hole acts like low-f lens: near/far points blur differently. |
| Tempo exposição | ↓ ∝ 1/d² | Handheld becomes possible; reciprocity failure less relevant. |
Território Artístico "Zone Plate"
Se drillar **multiple holes** ou **zone plate** (anéis concêntricos), obtém **lensless focusing** — sharp-ish images com halos wild. Not a pinhole anymore, but diffractive optic.
When to Go Large
- **Sujeitos moving** (people, wind-blown foliage) – need ≤ 1 s exposure.
- **Low light** (forest, indoor) – film speed limited.
- **Dream/impressionist aesthetic** – soft glow, halation, "Vermeer light."
When to Stay at d_opt
- Architecture, static landscape, test charts – maximum resolution.
- Scientific measurement (star positions, diffraction patterns).
Quick Experiment
Fazer três shims: 0.2 mm, 0.35 mm, 0.6 mm. Shoot same scene, same film. Scan & compare MTF. You'll *see* textbook curves in your own negatives.
Pinhole photography is only genre where **you manufacture the lens**. Own the variable.
