138 Holborn Bars
March 10th/41
My Dr Sir
We send you one of our metalic <sic> speculums, <1> of about seven inches focus parallell <sic> rays; with an aperture of about five and a half inches (this aperture can be increased some considerably <sic> without materially increasing the aberation <sic> of the reflector) – The box in which this reflector is placed – is rather short, it being originally intended for a shorter focus reflector – It will however answer your purpose, but should you find that the scattered light be a source of annoyance, you will have but to increase the length, infront <sic> of the present aperture – say some six or eight inches – it would be well to blacken the interior, and also to put a proper diaphragm to the addition: if found as above – viz, scattered light troublesome – The focus glass you will find inside of the reflector box = In adjusting the focus the ground surface of the glass must be towards the operator – should the slide, which carries the plate-holder move too stiff <sic>, you can ease it to your pleasure – should you desire to remove the reflector – remove the screw from the hook, at the small door, the speculum can them be removed if desired – A few trials of the focus glass will enable you to place and remove your prepared material quickly; Should you find that the im<ages?> <2> are formed too quickly – you can first adjust the focus, remove the glass, place a cut-off between the reflector and the filter, place your material in at a side door, after which (the filter having the proper expression) this cut-off could be removed the desired length of time, then closed; the material as acted upon, could be removed at pleasure
Your Very Respectfully
John Johnson
Wm H F Talbot <Esq>
Wm H. F. Talbot Esqre
No 31 Sackville Street
Notes:
1. John Johnson, of Saco, Maine, joined with Alexander S Wolcott to take a daguerreotype portrait in New York in October 1839. They soon opened a commercial daguerreotype studio there, using a reflector camera of Wolcott’s patent to shorten exposure times. In October 1840, Johnson sailed for London to market the camera there. He worked with John Goddard, and both men claimed to have discovered the use of iodine as an accelorant in the daguerreotype process. For his reminiscences, see “New York Correspondence” in The British Journal of Photography, v.15 n.421, 29 May 186, pp. 255–256.
2. Text torn under seal.