Photography: A Treatise on the Chemical Changes Produced by Solar Radiation, and the Production of Pictures from Nature, by the Daguerreotype, Calotype, and Other Photographic ProcessesS. D. Humphrey, 1852 - 290 pages |
Common terms and phrases
action of light albumen alcohol ammonia appear applied barytes beautiful blacken blue bromine calotype camera obscura chemical chloride chloride of silver chrysotype clean coating colour compound copper copy cotton Daguerre Daguerreian daguerreotype plate dark darkened dissolved distilled water drachms dried effect employed experiments exposed exposure fixed fluid ounce formed gallic acid glass grains heat hyposulphite of soda impression influence intensity iodide of potassium iodide of silver iodine iron lens liquid mercurial vapour mercury metal minutes muriate negative Niepce nitrate of silver nitric acid obtained operation ounce of water oxide paper perfect photogenic photographic photographic paper picture piece polished potash precipitate prepared produced quantity radiations rays removed rendered rotten stone rubbed sensibility shades sheet Sir John Herschel soaked solar solution of nitrate spectrum substances sufficient sunshine surface Talbot tint tion violet washed weak solution yellow
Popular passages
Page 46 - An Account of a Method of Copying Paintings upon Glass, and of making Profiles by the Agency of Light upon Nitrate of Silver ; with Observations by H. Davy.
Page 5 - It is so natural to associate the idea of labour with great complexity and elaborate detail of execution, that one is more struck at seeing the thousand florets of an Agrostis depicted with all its capillary branchlets (and so accurately, that none of all this multitude shall want its little bivalve calyx, requiring to be examined through a lens), than one is by the picture of the large and simple leaf of an oak or a chestnut. But in truth the difficulty is in both cases the same. The one of these...
Page 47 - The images formed by means of a camera obscura have been found to be too faint to produce, in any moderate time, an effect upon the nitrate of silver.
Page 46 - When the shadow of any figure is thrown upon the prepared surface, the part concealed by it remains white, and the other parts speedily become dark. For copying paintings on glass, the solution should be applied on leather ; and in this case it is more readily acted on than when paper is used.
Page 112 - ... a pretty strong blue impression is left, demonstrating the reduction of iron in that portion of the paper to the state of protoxide. The effect in question is not, it should be observed, peculiar to the ammonio-citrate of iron.
Page 48 - In conducting this operation, it will' be found that the results are sometimes more and sometimes less satisfactory, in consequence of small and accidental variations in the proportions employed. It happens sometimes that the chloride of silver is disposed to darken of itself, without any exposure to Light : this shows that the attempt to give it sensibility has been carried too far. The object is to approach to this condition as near as possible, without reaching it, so that the substance may be...
Page 152 - When the plate is well polished, it must be cleaned by powdering it well over with pumice and then rubbing it with dry cotton, always rounding and crossing the strokes, it being impossible to obtain a true surface by any other motion of the hand. The surface of the plate is now rubbed all over with a pledget of cotton, slightly wetted with the diluted nitric acid. Frequently change the cotton and keep rubbing briskly that the acid may be equally diffused over the silver, as, if it is permitted to...
Page 142 - For portraits out of doors, in the shade on a clear day, the time for sitting is from ten to fifteen seconds. " If the light is strong, and the view to be taken extensive, the operator should be cautious not to leave the paper exposed for a longer period than five or six seconds, as the picture will appear confused from all parts being equally acted on. In all cases, the shorter the time in which the picture is taken the better. " When the paper is removed from the camera no picture is visible. However,...
Page 46 - White paper, or white leather, moistened with solution of nitrate of silver, undergoes no change when kept in a dark place, but, on being exposed to the daylight, it speedily changes colour, and after passing through different shades of grey and brown, becomes at length nearly black.
Page 47 - In comparing the effects produced by light upon muriate of silver with those produced upon the nitrate, it seemed evident that the muriate was the most susceptible, and both were more readily acted upon when moist than when dry, a fact long ago known. Even in the twilight, the colour of moist muriate of silver spread upon paper slowly changed from white to faint violet; though under similar circumstances no immediate alteration was produced upon the nitrate.