NEGATIVE, in photography, is that kind of photographic picture in which the lights and shadows of the natural object are transposed; the high lights being black, and the deep shadows transparent, or nearly so. Negatives are taken on glass end paper by various processes, and should indiCate with extreme delicacy, and in reverse order, the various gradations • of light and shade which occur in a landscape or portrait. A nega tive differs from a positive inasmuch as in the latter case it is required to produce a deposit of pure metallic silver to be viewed by reflected light; while in the latter, density to transmitted light is the chief desideratum: accordingly inorganic reducing and retarding agents are employed in the development of a positive, while those of organic origin are used in the production of a negative. Adopting the collodion proc ess (which has almost completely replaced every other) as a type of the rest; time condi tions best adapted for securing a good negative may be briefly indicated, leaving it to the reader to apply the principles involved to any process he may desire to practice.
The possession of a good lens and camera hieing taken for granted, and favorable conditions of well-directed light being secured, all that is necessary is to establish a proper and harmonious relation between the collodion bath, developer, and time of exposure. A recently iodized collodion will generally be tolerably neutral, in which case. if the developer be at all strong, and the weather warm, the bath should be decidedly acid, or forging will be the result. Should the collodion, however, be red with free iodide; a merit trace of the will .suffice. while; the development may be much prolonged, even in want weather; WithOut fogging. If the simple fact be borne in mind that the presence of acid, either in the bath collodion or developer, retards the reducing action of the developer, it will suffice to guide the operator in mans- ditHeulties. The value of a negative consists in the power it gives of multiplying positive proofs. See POSITIVE PRINTING; also Pmyroonaenv.