DRAPER'S SECOND PORTRAIT LENS
As discussed above, Draper and Goode were unsatisfied with results of their five-inch lens. To
sharpen the focus but still allow the lens to pass a great deal of light, Draper exchanged his first
lens pair for a biconvex lens of four inches aperture and 14 inches focal
length. The wide diameter still passed much light. The longer focal length allowed greater depth of field (area of sharpness in the picture). The f
stop of such a lens would have been approximately f3.5 (Petzal's later
portrait lens was f3.6).
Draper used chromatic (non-achromatic) lenses. Chromatic dispersion became very noticeable in these lenses but Draper
made good plates by his knowledge, experience, and careful utilization of the principles of chemical focus. The chief difficulty he then faced arose from spherical aberration and narrow depth of field.
Draper admitted: "The risk of failure by employing an uncorrected
[chromatic] lens, is greater than the risk by a good achromatic, or a
reflector".[50]
Draper developed an outdoor and an indoor system of portraiture using this new lens of four
inches aperture and 14 inches focal length and described both in detail. Based on the evidence, it
appears that his work was probably limited to the period between 23 September and 7 October,
after which he appears to have temporarily dropped his work with the daguerreotype. The most
likely explanation for the cessation of his experiments is found in the dates of the school session at
the University of the City of New York. Classes began on 7 October. On the verge of beginning
his professorship at a new university, Draper probably accomplished all this portrait work before
classes began, then put aside his experiments until the end of session on 21 December[51*] No evidence has been found thus far to indicate that Draper
experimented during the fall session.
Only fragmentary and circumstantial information survives concerning the relationship
between Morse and Draper in late September and early October 1839, but it appears that their
contact with each other was limited. In later years both men mentioned collaboration, but virtually
everything they wrote concerned their partnership during the late winter and spring of 1840, six
months after the birth of American photography. It was not until the spring of 1840 that they
constructed a gallery made partly from glass on the roof of the University of the City of New
York.
The most compelling evidence of little interaction or collaboration between Morse and Draper in
the fall of 1839 comes from the journal Morse kept of his daguerreian experiments during January
and February 1840. In this journal, which is examined in more detail below, Morse recorded a
moment on 18 January 1840 when Draper taught him to use the chemical
focus. From that point forward in his record of daguerreian exposures Morse mentioned
focusing to the chemical rays.[52]
Morse's unfamiliarity with chemical focus before 18 January implies he had no close photographic
interaction with Draper before that date. From the spring of 1839 Draper's versatile technique
depended upon utilizing the difference between the visual and chemical focus
in chromatic lenses. Morse could never exactly say whether he or Draper successfully took
the first portrait because he was unfamiliar with Draper's work before the beginning of October.
One can imagine the surprise of both men when they discovered each other working on the same
project within the same building.
As mentioned above, it is significant that Seager's 3 October Morning Herald lecture
advertisement omitted Draper's name, although it mentioned Morse, Chilton, Stephens, and Duer.
If, indeed, Draper's work initially went unnoticed by Seager, Morse, and Chilton, it is possible that
Seager's advertisement inspired Draper and Goode to contact the other experimenters. In this
scenario Morse and Draper might have briefly met in the first days of October and observed each
others instruments and product.
To summarize, between late September and 7 October, Draper perfected methods to take portraits
indoors or outdoors with the second lens he used in his experiments to take portraits--his single,
bi-convex lens of four inches aperture and 14 inches focal length (approximately f 3.5). In
late September and early October Morse used only a standard achromatic daguerreian lens of
about f 15. His lens produced distant, rooftop photographs of his daughter and friends. Their eyes
were closed, through an exposure time of ten to twenty minutes.[53*]