Plain directions for obtaining photographic pictures : upon waxed and albumenised paper and glass, by collodion and albumen : including a third edition of Le Gray's Treatise on photography, a description of the stereoscope and the manner of taking pictures suited for it : also, the process for copying microscopic objects, &c. (1852)
Heisch, Charles, Le Gray, Gustave, 1820-1882 · London : T. Willats · leaf 71
alternately predominating either partially or wholly over the disc. In the same manner the mind perceives no trace of violet when red is presented to one eye and blue to the other, nor any vestage of orange when red and yellow are separately presented in a similar manner. These experiments may be… … Fig 9. Fig. 9 represents another form of the stereoscope in which the observer looks directly at the drawings instead of at their reflected images ; the two being made to coalesce by the introduction of two prisms or semi-lenses into the eye-pieces of the instrument. This form possesses th«…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
