A pinspeck camera is the complement, or anti-pinhole, of a pinhole camera, using an opaque dot in a clear aperture instead of a small hole. Each object point casts the dot's shadow onto the image plane, producing a weak negative image.
Principle In a pinspeck camera, image formation occurs through selective blocking rather than transmission: each object point casts the shadow of the opaque speck onto the image plane. Torralba and Freeman describe the same complementary effect for an occluder, whose cast shadow can contain a negative image of the surrounding scene rather than only the occluder's silhouette.
External links Jearl Walker The Pleasure of the Pin Hole Camera and Its Relative the Pinspeck Camera Adam Lloyd Cohen Anti-pinhole imaging Optica Acta: International Journal of Optics Volume 29, Issue 1, 1982 Antonio Torralba and William T. Freeman Accidental Pinhole and Pinspeck Cameras M. Young Quantum noise limits the pinspeck camera to simple objects Johannes Grebe-Ellis and Thomas Quick Soft shadow images