Standard developer.
Perhaps the simplest advice we can give as to the particular developer to be used is to take as the normal developer one mixed according to the formula sent out with the plates which the student has chosen to work with, but the student must not use it in the exact proportions given by the maker. Let the student mix up the stock solutions as told, varying the constituents as the case in hand demands. If he has carefully and thoroughly read his chemistry, and if he remembers the hints we have given him, he will have no difficulty in following out the directions.
He should, as a rule, never use more than two-thirds of the amount of pyrogallic acid recommended; let him be very careful how he uses the restrainer, and let him add the ammonia only in small quantities, unless the exposure has been very rapid. As a rule let him work with weak developers. We could easily give a dozen or even fifty formulæ for developers, but the student would be no wiser if we did, only more confused. Every photographer fancies his own particular formula, but we have no belief in any special favourites; we have worked with many, and find the results depend altogether on the quantities used and the manner of developing rather than on the constituents. Take, then, the formula recommended by your plate-maker, but use it, as we have said, with judgment. Begin with a sufficiency of pyrogallic acid (according to the subject), use little restrainer, except in over-exposure, and add the ammonia slowly, adding a few drops from time to time as required. In short, make it your rule to use weak developers, and develop slowly. If you think you are likely to have under-exposed, add ten to twenty drops of a one per cent. solution of hyposulphite of soda, using no restrainer. Some unscientific persons imagine that development can be reduced to a science, and that absolute quantities of each solution must be used. One might as well expect a physician always to prescribe the same doses. Each picture requires a developer of its own; that should never be forgotten. We have tried hydrokinone instead of pyrogallic acid; a given quantity of hydrokinone does the work of double that quantity of pyrogallic acid, but it has no advantages, so far as we can see, except for the development of under-exposed plates. For very rapid work we recommend the carbonate-of-potash developer, as green fog does not result. |Eder’s potash developer.|The formula we use is Dr. Eder’s:—
| A. | ℞ Pure dry mono-carbonate of potash | 90 | parts |
| Water | 200 | ” | |
| B. | Pyrogallic acid | 12 | ” |
| Sulphite of soda | 25 | ” | |
| Citric acid | 1½ | ” | |
| Water | 100 | ” |
Before using, mix forty to sixty drops of A with three ounces of water, and the same quantity of B. We generally use more water than that recommended in the formula.
Now it will be remembered that in bright sunny effects brilliancy, and therefore density, is needed; the gamut of light and shade is not so extended as in some subjects, for the shadows are bright with reflected light, but the whole must be brilliant and in a high key. In our opinion Dr. Eder’s potash developer gives this better than any other. For snow scenes, on the other hand, where there are often very black heavy shadows, we recommend, as we have done before, the developer given by the maker of the plates, used in a weak solution.
Local development.
No photographer need hope to obtain perfect results and exactly what he wishes, without resorting to local treatment; and here once more the knowledge of the artist steps in and places him at an advantage over the craftsman, but no one without sound art-knowledge should attempt this local development. On the other hand, with a thorough knowledge of the tonality of his subject, the artist can, by local development, so modify his work that he will be able to obtain wonderfully true results. Let us imagine such a subject as a dark tree in the foreground of a landscape with a bright delicate distance. No manner of development will bring these into true relation unless local treatment is resorted to. Unfortunately, directions cannot be given for this work, for each subject will of course require special treatment; the rationale of the practice, however, is founded on the general chemical principles of photography. For use in local development, then, it is always wise to keep a series of small paint-brushes at hand. All three developers may thus be used locally with great effect. During local development, the plate should constantly be re-plunged into the developer, so that the local development may not show. We strongly recommend the student always to develop by artificial light, for by this method he will have a more regular standard to judge of the quality of his negative than if he trusts to the varying strength of daylight.
The best way of judging of the tonality of a negative is to hold it up from time to time before the light of the developing-room; correct judgment on this matter can, however, only be obtained by long experience. The student will be told in the printed directions—supplied with many plates—that if the image does not come up in 10 or 15 seconds, the plate has been under-exposed. This is not our experience, and, as a rule, the image takes longer to show than the time named. We prefer to judge by the way the image comes up. If the highest lights come up very sharply defined and turgid, then the plate is under-exposed, but if they come up delicately, and detail begins to appear gradually over the various parts of the plate, all is well. But all this will only become familiar by experience. By constant habit the student will mentally run over the facts of the problem before him, as does a physician, and proportionately to his skill will he apply the right remedy at the right time.
After treatment of plate.