Ibn al-Haytham's Pinhole Camera (Qamara)

Qamara Geometry

Object distance d_o 6.0

Screen distance d_i 3.0

Aperture diameter D 0.30

Live Readouts

Magnification |m| = d_i/d_o

0.50×

Image height h_i

1.50

Geometric blur diameter b = D·(d_o+d_i)/d_o

0.15

How it works

Around 1011–1021 CE in Cairo, Ibn al-Haytham (Alhazen) wrote the Kitab al-Manazir (Book of Optics), the first text to correctly explain vision as light entering the eye rather than rays leaving it — and to give a rigorous account of the qamara (dark chamber / camera obscura): light travels in straight lines, so rays from every point of a lit object that pass through a small hole reconstruct an inverted image on the far wall.

Similar triangles across the aperture:
  h_i / h_o = d_i / d_o      (image is inverted: sign flips)
  magnification  |m| = d_i / d_o
  image height   h_i = h_o · d_i / d_o

Finite-aperture blur (each point becomes a small disc,
the aperture's own shadow scaled up by the far triangle):
  blur diameter  b = D · (d_o + d_i) / d_o

d_o / d_i sliders — move the glowing "F" object or the screen; watch the image invert left-right and top-bottom and rescale exactly as the similar-triangle formula predicts.
Aperture diameter — a wider hole lets in more light but every source point now casts a small blurred disc instead of a point, exactly the resolution/brightness trade-off al-Haytham described when narrowing the qamara's opening sharpened the image.
Show aperture blur cones — traces several rays sampled across the aperture's edge (instead of one ray through its centre) for a few reference points, revealing the penumbra cone whose width on the screen is the blur diameter above.

This straight-line, small-aperture imaging principle is the direct ancestor of every camera — pinhole, film, or digital sensor — built since.

Object (F, lit) Inverted image on screen Wall & pinhole

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