Wednesday, August 13, 2008

National Development.

There are many ideas as to what is the correct way of developing a negative, and the exponents of each claim that theirs is the true and only way. There is no accepted standard for goodness in a negative, which is perhaps a good thing, for its absence allows of individuality in the finished result, although this must not be confused with "fluking," which is what happens when an operator aims at one effect and obtains quite another, which he is astute enough to put forward as a premeditated piece of work. The clever photographer is the man who starts with a definite idea for a picture and by skilled technique realizes it in a print. To do this one must have perfect control of exposure and development. The best lighted figure may be made either hard or flat by incorrect exposure, while a correctly exposed plate may be made to yield a thin soft image or a dense harsh one by injudicious development.
To ensure even quality it is very necessary to keep to one brand, and preferably one grade of plate. The best technician in the world could not produce a dozen negatives of even quality from twelve plates of different makes and rapid ties even if all had received an equivalent exposure. Plates vary greatly in the time taken for development and in the appearance of the image before fixing. A common way of judging the progress of development is to look for a trace of the image on the back of the plate. This can only be done if one brand of plate is in use, and then only to a limited extent, as this method is quite upset by variations in the thickness of the emulsion coating. While upon this subject it may be useful to correct an error sometimes made, which is, that when the image is clearly visible on the back of the film, the utmost density which the plate will give has been obtained. We had a case under our notice some few months ago where the operator proposed to change his plates, because, although he developed them right through to the back, the images were always thin. On our suggestion he allowed some plates to remain in the developer for three minutes longer than others, which he fixed at 3 usual times, and was convinced by the difference in density that his development had always been carried on for too short a time.
One of the old errors was that the best results could only be obtained by what was known as "tentative development." This meant starting the development with a minimum of alkali, which was gradually added as needed. There was some reason for this when ammonia was used as the alkali, as volatilization rapidly reduced activity of the solution, and fresh ammonia was needed to complete development. When the fixed alkalies in the form of the carbonate of soda and potash came into general use the “working up" by adding small quantities of alkali to the developer fell into disuse, although a few old-fashioned workers still practice it.
It is not our purpose to recommend any particular developing agent as superior to the others. Some developers have the reputation of giving thin images and others plucky ones, but this is largely a question of dilution and temperature. Next to exposure, this decides the possibilities of the negative, coney’s length of development with any given solution. With normal exposures short development gives a thin flat negative and development gives the maximum of density and contrast. Between these extremes the operator must choose for himself. All non-staining developers, such as am idol, hydroquinone, and many others yield a negative of which the printing quality is due to reduced silver only, but pyro behaves differently, the silver image being reinforced by the "pyro stain." It is generally acknowledged that a pyro-developed negative will usually give a more brilliant print than one of apparently similar density, but free from stain. This is due to the fact that the stain is deposited in proportion to the density of the image, and is not uniform all over the plate. If such a negative be dissolved away, by using Farmer's reducer, it will be that a thin brownish-yellow image remains.
One of the commonest errors in development is to over- develop under-exposed plates, and to under-develop over- exposed ones This is caused in the first place by the desired to force out all possible detail in the shadows, the result being that the high lights are made so dense that any shadow detail is lost in the necessary depth of printing. In the second case the over-exposed plate is under- developed because the whole surface of the film quickly blackens, and the operator fears that the detail will become buried. This is quite wrong; the proper course is to develop for the full normal time, and to dissolve away the fog with the ferri-cyanide reducer. It may be noted here that it is of little or no avail to add bromide to the developer after the image is well out; to be effective, bromide should be added to the developer before pouring on the plate.
The degree of dilution of the developer has an important effect upon the negative. A weak solution can be used until all the details of an under-exposed plate are brought out, without obtaining too much intensity in the high-lights. Concentrated solutions give the maximum of contrast, especially when a little bromide is used in addition.
Too prolonged development will give a general chemical fog, and an excess of alkali often added in cases of under- exposure has the same effect. A disagreeable colour, not quite a fog, is caused by putting plates developed with am idol or metol direct into the fixing bath without rinsing. With pyro the fixing bath rapidly becomes discolored, but with the non-stain developers a large quantity of solution can be carried over into the fixing bath without altering the colour very much.

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