Hand Camera Harmonising Harsh Negatives
Hand Camera. See Detective or Hand Camera.
Hardening of Gelatine Films. See Formalin.
Harmonising Harsh Negatives. This process is a very valuable one, and should be far more frequently used than it is. It will reduce the dense parts of a harsh negative and intensify weak parts. By means of this process it is possible to obtain a really decent print from a negative of a church interior which is almost a mass of halation, and passable prints may be obtained from harsh under-exposed negatives. It was suggested first by Eder in 1883. The negative, after being fixed and well washed, should be soaked in a solution of
Potassium bichromate ... ... .... 1 part.
Hydrochloric acid ... ... ... ... 3 parts.
Alum ... ... ... ... ... ... 5 ..
Water ............... 100 ..
In this the negative gradually turns white, and care must be exercised that it is thoroughly bleached from the back as well as the front. The negative must now be thoroughly washed in running water for at least two hours, or repeated soaking, film downwards, in frequently changed water for at least four hours. The bleached plate may now be redeveloped, either with an old hydroquinone developer or with ferrous oxalate. This is the important point in this process, for development must only be carried on till the details in the shadows are fully developed, and not till the high lights are developed right through, or in the latter case no improvement will be seen. As soon, then, as the details in the shadows and half-tones are developed, the plate may be rinsed and refixed. There being still some undeveloped chloride of silver at the back of the dense parts, this is fixed out, and the negative will be found by no means so hard as before. I have stated that this process in-tensifies the shadows, and this is only, strictly speaking, true when the bleached plate is exposed to daylight for some time and then developed, the chloride of silver image then being con-verted into a more nonactinic character than previously. An alternative method due to Mr. J. Mcintosh is the following. Prepare the following solution : -