NEGATIVE MAKING photography be practised as taught in the method herein presented, Le.— with due consideration to the actinicity of the sur faces photographed and with a knowledge of the inertia exposure to be given in each case, it may easily be realized that development is almost purely mechanical in its nature. This is prac tically true and in fact has been demonstrated in the previous chapter. The author, in the practice of home portraiture, works under vastly different conditions of light from hour to hour and uses roll film, never seeing an image on the ground glass, but because the light is measured in each case and a correct exposure given the development of these films are safely entrusted to an assistant who at the start had had no ex perience whatever in photography. This assist ant was shown how to handle the strips of film properly and was told that the water should be cool, the developer always of a certain strength and the development carried on for a given time. When the films are thoroughly fixed the author takes them in hand to make the minute alter ations with the reducer and intensifier, which work, as will be shown, is considered not so much a corrector of errors as a recognized part of the real work of placing the negative when finished at the desired point of opacity and contrast.
The folly of expending mental effort on methods of exact development is seen by the ac companying illustration in which three films were given like normal exposures (Plate XII). One of them was then developed for four minutes, another for eight minutes, the normal time for the developer used, and the other for twenty four minutes. Otherwise than this variation in time the conditions were uniform throughout for all three negatives. When the negatives were fixed the over-developed one was reduced to the desired opacity, or as near as possible to that of the normally developed one, and the under-developed one was intensified to the same opacity. Each of these processes required but a few minutes to perform. The three illustra tions by their similarity, prove that it is prac tically indifferent how long correctly exposed emulsions remain in the developing solution so long as they are afterwards brought to their correct density by reduction or intensification. This of course is quite consistent with the "law of constant density ratios" discussed before (chapter VIII). Since both developers and
emulsions vary as to the speed with which they develop it is seen to be useless to com plicate the worker with any special system of developing.
As has been insisted, the relation of the grada tion steps is fixed in the exposure and the prac tical point to be attained in development is simply to approach an opacity and contrast suitable for the printing medium to be used and the tone gradation desired. This opacity may sometimes much better be secured in the light by the use of a ,reducer or an intensifier than be sought for over-carefully in the dark room in the devel oping solution, as plate XII proves.
It should be realized that the work of devel oping an emulsion of which the inertia has been overcome in the exposure a known number of times is entirely different in character from developing one of which the exposure has been estimated and which must be watched for signs of under- or over-normal exposure. This certainty in development, made possible by known and predetermined exposure, when fully realized will justify the opinion of the author that development is the one branch of photo graphic labor which is practically mechanical, the result simply proving that previous work has been well comprehended and executed.
Whatever method of development be employed care should be taken to use a solution of normal strength at a temperature close to F. or The time of development should be gauged so as to secure as near as possible the opacity de sired in the negative or negatives being devel oped, in view of the contrast of the paper or other medium in which the picture is to be printed and also of the tone effect desired. This is simply for the convenience of avoiding as much as possible the work of after treatment. On using any formula as given, should the time required to develop a negative be less than three or four minutes it is advisable to increase the quantity of water in the formula until a development of about five to six minutes gives the correct or approximate density. The reason for this is to give the emulsion time enough to become thoroughly impregnated with the developing agent, and thus avoid lack of uniformity in the result. The developing solution should be used but once.