transparent camera



illustration: comparison of eye and camera obscura, early eighteenth century

Descartes’s description of the camera obscura in his La dioptrique (1637) contains some unusual features. Initially he makes a conventional analogy between the eye and the camera obscura:

Suppose a chamber is shut up apart from a single hole, and a glass lens is placed in front of this hole with a white sheet stretched at a certain distance behind it so the light coming from objects outside forms images on the sheet. Now it is said that the room represents the eye; the hole the pupil; the lens the crystalline humour…

But before proceeding further, Descartes advises his reader to conduct a demonstration involving “taking the dead eye of a newly dead person (or failing that, the eye of an ox or some other large animal)” and using the extracted eye as the lens in the pinhole of a camera obscura. Thus for Descartes the images observed within the camera obscura are formed by means of a disembodied cyclopean eye, detached from the observer, possibly not even a human eye. Additionally, Descartes specifies that one

cut away the three surrounding membranes at the back so as to expose a large part of the humour without spilling any … . No light must enter this room except what comes through this eye, all of whose parts you know to be entirely transparent. Having done this, if you look at the white sheet you will see there, not perhaps without pleasure or wonder, a picture representing in natural perspective all the objects outside.

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