A Manual Of Photography

CHAPTER VIII. PORTRAITURE BY THE DAGUERREOTYPE. When Daguerre published his process, a period of twenty minutes was required to obtain a good copy of any external object: hence this period was far too long to admit of its being employed for portraiture. Mr. Towson, of Devonport, in a very valuable paper which appeared in the Philosophical Magazine in 1839, offered several suggestions on the use of large lenses, &c. which he supposed might lead to the use of the daguerreotype for the purposes of portraiture. Dr. Draper, of New York, acting on the suggestions of Mr. Towson relative to the adjustment of the focus, succeeded in accelerating his process so far as to obtain portraits from the life. He published his process in the London and Edinburgh Philosophical Magazine for September 1840. From this paper 1 shall take the liberty of making copious extracts. It was first stated that it was necessary, to procure any impression of human features on the daguerreotype plate, to paint the face white, or dust it over with a white powder, it being thought that the light reflected from the flesh would not have sufficient power to change the iodized surface. This has been shown to be an error, for, even when the sun shines but dimly, there is no difficulty in obtaining a correct delineation of the features. “When the sun, the sitter, and the camera, are situated in the same vertical plane, if a double convex non-achromatic lens of four inches diameter and fourteen inches focus be employed, perfect minatures can be procured in the open air in a period varying with the character of the light from 20 to 90 seconds. The dress also is admirably given, even if it should be black; the slight differences of illumination are sufficient to characterise it, as well as to show each button and button-hole, and every fold. Partly owing to the intensity of such light, which cannot be endured without a distortion of the features, but chiefly owing to the circumstance that the rays descend at too great an angle, such pictures have the disadvantage of not exhibiting the eyes with distinctness, the shadow from the eyebrows and forehead encroaching on them. To procure fine proofs, the best position is to have the line joining the head of the sitter and