PAPERS FOR BEGINNERS, NO. 9.
TREATMENT OF UNDER-EXPOSED PLATES
By an "under-exposed plate" is meant a plate which has not been exposed long enough to the action of light for the objects to make a deep enough impression in the silver salts, or to cause the chemical change to take place which makes the perfect picture.
The normal development of an under-exposed plate results in a negative in which the high or white lights are very strong, and have a chalky appearance in the print, while the shadows have little or no detail; and where a plate has been much under-exposed, only clear glass is the result of the development. The reason why the high lights appear so harsh and strong is due to the fact that to get detail in the shadows the development is carried on till the high lights are very much over-developed and the film has become dense.
The practised amateur usually knows whether his plate has been under-exposed or not, and treats it accordingly. The beginner, not having learned how to gauge exposures correctly, must learn how to distinguish an under-exposed plate as soon as the developer begins to act on it, so that he may get a good, or fairly good, negative.
If a plate which has been under-exposed is placed in a normal developer, the high lights will be some time in coming out, and the shadows will not appear at all, or, if they do, will be very dim. If the development is continued in order to bring out detail, the plate is apt to fog, and is then spoiled entirely.
If the rest of the image does not follow the high lights in a reasonable length of time, take the plate from the developer and place it in clean water. It will do no harm if it stands in water for a few minutes, for water will bring out detail in an under-exposed plate.
Nothing has been said about the different kinds of developers, though they will be fully treated in later papers. The beginner should stick to one developer till he has learned just how to use it.
If one is using pyro, a fresh solution should be at once made up, using half the quantity of pyro given in the formula, and the full amount of the alkaline solution. The pyro is the developing agent, or that which gives the required strength or density, while the alkaline solution, containing the sulphite of soda, prevents the staining of the negative and preserves the pyro. After the development of the plate is finished turn off the solution, leave the plate in the tray, pour water over it, and allow it to stand for fifteen or twenty minutes, being careful that it is covered from the light.
If one uses hydrochinon, which is a favorite developing agent with amateurs, dilute the developer and add from three to seven drops of iodide solution. This solution is composed of 1 grain of iodine, 1 ounce of water, 1 ounce of alcohol. Mark the bottle "Accelerator." This solution hastens the development of the image and brings it up evenly, and the contrasts between the lights and shadows are made soft and delicate.