Boulogne-sur-Mer: Imprimerie de Charles Aigre, 1858. First edition. 8vo., 22 pp., plus two folding plates. Later cloth and marbled boards. Neat library deaccession stamp of S. F. P. (Société Française de Photographie.) Tiny closed tear at the gutter between the first blank and title page. Very good. Item #26470
The authors offers a mathematical formula for determining exposures required by various portions of the spectrum. No copy located by Roosens and Salu. OCLC locates a single copy at BM Lyon.