قراءة كتاب Photography in the Studio and in the Field A Practical Manual Designed as a Companion Alike to the Professional and the Amateur Photographer
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Photography in the Studio and in the Field A Practical Manual Designed as a Companion Alike to the Professional and the Amateur Photographer
saturated, then add the alcohol. Excite with p27
| Iodide of Ammonium | 3½ grains to ounce |
| Iodide of Cadmium | 2 |
| Bromide Cadmium | 2½ |
Collodion sometimes, from long keeping, loses sensitiveness and becomes of a deep red color. When such is the case, it should be set aside and fresh samples prepared, which would be improved in working quality by the addition of small quantities of the old, and thus old stock may be used up without deterioration in the work.
Negative collodion should not be so heavy bodied or thick as that for positives; neither should it be so highly excited. Good positive collodion should have as many as 8 grains of the iodides and bromides to the ounce, requiring a silver solution not lower than 50 grains strong and going somewhat higher in cold weather.
The standard silver solution for negatives is 45 grains of silver nitrate to the ounce of water and the collodion from 5½ to 6½ grains to the ounce, with a tendency to less in cold weather.
Collodion for negatives should be permitted to ripen a day or two before using, unless it is brought to that state by mixing with old.
NEGATIVE COLLODION. C.
| Iodide Ammonium | 192 grains |
| Bromide Cadmium | 128 |
| Bromide Potassium | 96 |
| Ether and Alcohol | 32 oz. each |
| Cotton | 320 grains |
The preceding formulæ are for portrait work in studio. For other work, such as outdoor views, p28 landscape or architectural, or for copying engravings, etc., certain modifications of the collodion, to produce greater intensity or more contrast, are desirable. Collodion suitable for such purposes can always be purchased from the photo stock dealer, in quantities desired, and for that reason it is not best for the amateur nor the professional photographer either, to prepare small samples for special purposes. If it should, however, be found at any time necessary to prepare such a collodion, the second formula of Negative Collodion A will be found suitable for views of buildings, copies of engravings and such like work.
It was at first thought to be unnecessary to give a formula for the preparation of pyroxiline or gun cotton, as no individual not in the business can possibly produce an article that can be in any way compared to that made by manufacturers of skill and experience.
For the benefit of any one wishing to experiment, this formula is given: