Leonardo compared the camera obscura’s image-stream to a painting not only because it, too, was a picture, but also because photography and painting were pictorialized at the same time: in the quattrocento, and the first part of the cinquecento. They were also pictorialized in a similar way. The camera obscura’s image-stream, which had until then served as the transparent medium through which to watch a solar eclipse without injuring one’s eyes, became visible in and of itself. And painting gradually liberated itself from the ritual, pedagogical and illustrative uses to which it had until then been put, and the pre-given spaces on walls and ceilings that it had been expected to fill, and descended to the ground. It found its way onto an easel, and then onto a different kind of wall. It continued to be a site where other things appear, but it also became visible in a new way: as a thing-in-the-world, like other things and among other things.
This visibility became even more evident after it migrated to the second wall--so much so that it extended outward, to include the beholder that its Being required. Since this space was one into which anyone could step, the somebody became everybody, and the process by means of which a painting becomes a picture was finally complete. It became what photography had always been: double-sided. But it also achieved something that would not be possible within photography for another three centuries: it became a two-person picture.
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