The sciopticon manual : explaining Marcy's new magic lantern, and light, including magic lantern optics, experiments, photographing and coloring slides, etc. (1874)
Marcy, L. J., author · Philadelphia : L.J. Marcy · leaf 35
25 SCIOPTICON MANUAL of radiation would lose intensity with distance, and so a lens of short focus, being nearer, would bring more light … to bear on the image. But the light in fact proceeds from l , and what passes through the condenser and picture becomes a cone of light, with its apex in the objective. This cone of light must be regulated by the position or power of the condenser so as to fall within the compass of the objective.…
Lantern projection · Slides (Photography)
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
