Exposure times for the earliest daguerreotypes ranged from three to fifteen minutes, making the process nearly impractical for portraiture. Modifications to the sensitization process coupled with the improvement of photographic lenses soon reduced the exposure time to less than a minute.
Although daguerreotypes are unique images, they could be copied by redaguerreotyping the original. Copies were also produced by lithography or engraving. Portraits based upon daguerreotypes appeared in popular periodicals and in books. James Gordon Bennett, the editor of the New York Herald, posed for his daguerreotype at Brady's studio. An engraving, based on this daguerreotype later appeared in the Democratic Review.
The Cameras
The earliest cameras used in the daguerreotype process were made by opticians and instrument makers, or sometimes even by the photographers themselves. The most popular cameras utilized a sliding-box design. The lens was placed in the front box. A second, slightly smaller box, slid into the back of the larger box. The focus was controlled by sliding the rear box forward or backwards. A laterally reversed image would be obtained unless the camera was fitted with a mirror or prism to correct this effect. When the sensitized plate was placed in the camera, the lens cap would be removed to start the exposure.
Daguerreotype Plate Sizes
- Whole plate 6-1/2" x 8-1/2"
- Half plate 4-1/4" x 5-1/2"
- Quarter plate 3-1/4" x 4-1/4"
- Sixth plate 2-3/4" x 3-1/4"
- Ninth plate 2" x 2-1/2"
- Sixteenth plate 1-3/8" x 1-5/8"
