Digital camera obscuras

Abstract

A camera obscura is a darkened chamber in which an image of the scene outside the chamber is projected by a pinhole or other optic onto a screen within the chamber. Early obscuras used pinhole optics, but by the 16th century obscuras with lenses became popular as aids for drawing or painting scenes with the correct perspective. By the late 19th century, the screen had largely been replaced with photo-sensitive materials, and film cameras replaced obscuras. Over the last few decades, digital cameras using electronic sensors have replaced those using film. However, large projections can have significantly different properties from small projections, and it is very difficult to build a large digital image sensor. Thus, there is interest in using a small-sensor digital camera to photograph the large screen of a obscura. For example, it is relatively easy to obtain much shallower depth of field using a large screen, but a small sensor photographing the screen essentially copies that depth of field, so obscuras have often been used as “bokeh adapters” for small-sensor digital cameras. The current work is an experimentally-grounded exploration of the issues that arise in construction of digital camera obscuras, their use, and exposure control and postprocessing of digital images captured using a small sensor to photograph the image projected on an obscura’s screen.