[draft:]
for ye Sol Genl
May 14/51
I wd begn by defing wh is mt by pos & neg photogrc picts.A pos pict is 1 in whch ye lights of ye nat objt copied depicted obt or scene are represd by lights & the shads by shades- A neg pict. is ye reverse of this, tht is t say, one in wch ye lights of the object are repr. by shades, & ye shadows by lights. Thus for example the neg pict. of a printed book, is one in wch ye paper wd be represd black & the types white.
This being premised, I proceed to explain that hitherto, [illegible deletion] photogrc picts of any objects made upon glass, have been negve ones; & that in order to obtain posve pictures thereof, it was necessary to copy them. For this copy, reversing ye lights & shades of the first obtained picture, made them conformable to the original object.
A patent was granted to myself & Malone last year for an improvement upon this process , . <1>
We discovered and pu described a method of converting the negative picture into a posve one by a subseqt process; thus retaining ye identi ty cal picture first made, but requiring [illegible deletion] an additional process in order to obtain the positive result.
My present inventn consists in a new process method by which I obtain positive pictures upon glass by a single process, & it has the collatl advantage of being very much more rapid in its actn than any process upon glass hitherto published upon and therefore is eminenty suited for taking portraits, which require the use of the quickest processes that can be devised. <2>
My invent process consists in washing glass a sheet of glass successively with white of egg. nitr. silv-again white of egg- iod. iron, and again with a much stronger solutn of nitr. silv. drying the glass between each wash. This then is a fit state to receive the impression upon it placed in a camera, & exposed to the light of any object, of wch it quickly receives an image. This image wch at first is hardly visible, is washd with sulph iron, which renders it plainly visible: fix with hypo and finally well washed with water.
And with respect to likewise another improvement in taking Photogrc portraits, namely in illuminating the countenance of ye sitter with a strong electric light obtain’d by the discharge of an Electrical battery. This light, wch is as momentary as that of a flash of lightning, enables the expression of the features to be depicted, although the image of an object to be photographically depicted, although that object was in motion at the time the electric battery was discharged. <3>
[expanded version:]
14 May 1851
for the Solicitor General
I would begin by defining what is meant by positive and negative photographic pictures. A positive picture is one in which the lights of the natural object copied depicted object or scene are represented by light and the shadows by shades. A negative picture is the reverse of this, that is to say, one in which the lights of the object are represented by shades, and the shadows by lights. Thus for example the negative picture of a printed book, is one in which the paper would be represented black and the types white.
This being premised, I proceed to explain that hitherto, photographic pictures of any objects made upon glass, have been negative ones; and that in order to obtain positive pictures thereof, it was necessary to copy them. For this copy, reversing the lights and shades of the first obtained picture, made them conformable to the original object.
A patent was granted to myself and Malone last year for an improvement upon this process. We discovered and described a method of converting the negative picture into a positive one by a subsequent process; thus retaining the identical picture first made, but requiring an additional process in order to obtain the positive result.
My present invention consists in a new process method by which I obtain positive pictures upon glass by a single process, and it has the collateral advantage of being very much more rapid in its action than any process upon glass hitherto published upon and therefore is eminently suited for taking portraits, which require the use of the quickest process that can be devised.
My invent process consists in washing glass a sheet of glass successively with white of egg, nitrate silver - again white of egg - iodide iron, and again with a much stronger solution of nitrate silver drying the glass between each wash. This then is a fit state to receive the impression upon it placed in a camera, and exposed to the light of any object, of which it quickly receives an image. This image which at first is hardly visible, is washed with sulphate iron, which renders it plainly visible: this with hypo and finally well washed with water.
And with respect to likewise another improvement in taking Photographic portraits, namely in illuminating the countenance of the sitter with a strong electric light obtained by the discharge of an Electrical battery. This light, which is as momentary as that of a flash of lightning, enables the expression of the features to be depicted, although the image of an object to be photographically depicted, although that object was in motion at the time the electric battery was discharged.
Notes:
1. This was Patent No. 12,906, Photography, sealed 19 December 1849 and granted to WHFT and Malone, 18 June 1850. WHFT was granted a disclaimer on this patent on 26 April 1855.
2. This was WHFT's Amphitype process - see Doc. No: 06408. WHFT was granted Patent No. 13,664 for this on 11 December 1851 and granted a partial disclaimer on 12 June 1851.
3. WHFT first demonstrated this concept at the Royal Institution on 14 June 1851, when he arrested the image of a printed page being rotated at speed on a disk - see his description of this experiment to Michael Faraday in Doc. No: 06429. A summary was published as an 'Important Discovery in Photography' in the Literary Gazette, no. 1797, 28 June 1851, p. 443. This invention was covered under his Patent No. 13,664, 11 December 1851.