This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Preparing The Apparatus For Daylight Work. The drawing of the daylight Bromide Enlarging Apparatus, reproduced herein, serves to illustrate the use of a hand or view camera for negative enlarging. The camera is arranged before the window in exactly the same manner as for Bromide enlarging, only you must be more particular about having the room perfectly dark. This is important, as the dry plate which is to be used is about twenty times more sensitive than the Bromide paper, and if the room is not perfectly light-tight there is danger of fogging the plate.
The Easel. For the easel, you may use an ordinary box, or construct a regular easel as shown in Illustration No. 56. In either case instead of covering the easel with white cardboard, cover it with a dark cardboard, or dark paper, as the dry plate is so very sensitive, that the white cardboard will cause halation, and probably fog.
Focusing. Place the transparency in the camera, in exactly the same manner followed for Bromide enlarging, with the film side facing the lens. Place the easel directly in front of the camera and within two feet of it. Rack out the bellows, or move the easel backward or forward, until the desired enlargement is obtained. The size is controlled by the distance between the lens and the easel. In obtaining the focus, attach to the easel a white card of the same size and thickness as the plate to be exposed. This will give a perfect focus. To attach this card use thumbtacks, as they have larger heads, and will hold the card more firmly.
823. Place a tack about one inch from each corner of the bottom of outline of the negative on the screen, indicating where the card should be placed. These tacks serve as a support, and hold the card firmly, and also indicate where the sensitized plate must be placed. After obtaining the focus, attach the plate to the screen. First, however, cap the lens, or close the shutter, and exclude all light from the room. Remove the cardboard, take the plate to be exposed and place the lower edge upon the thumb-tacks, adjusting it to the same position occupied by the cardboard. Place another thumb-tack at the top, at the center of the plate, to hold it securely for the exposure.
824. When a little light for the arranging of the plate is desired, use a ruby-lamp within a few feet of the easel. This is not often necessary as the plate can usually be arranged without a light of any kind.
Exposure. The exposure depends on the quality of the transparency, and the strength of the light employed. A medium strength negative may require four seconds exposure, or it may require eight seconds, all depending upon the nature of the illuminant. A hard or contrasty negative will require double the exposure of a soft snappy one, and where artificial light is employed, four times the exposure necessary for daylight will be required.
826. The exact time can only be ascertained by experience. It is best for the first experiments to use a plate of small size. Place it in the center of the enlarged image; with a cardboard, cover one-half of this plate and give four seconds exposure; then remove the cardboard and give the entire plate four seconds more exposure. One-half the plate will have been exposed four seconds and the other half eight seconds. Develop this plate, and the result should indicate the necessary exposure. If the half given four seconds exposure is fully-timed, the portion given eight seconds exposure will be fogged and flat. If, on the other hand, the portion given four seconds exposure is found lacking, and not strong, this will indicate that it was insufficient. Should the portion given eight seconds be full of detail and of good strength, it will show that eight seconds is nearly the correct exposure. In a word, the result of this experiment will determine the proper exposure required for the transparency being used.
STUDY Study No. 14-See Page 358 Alfred Holden.