Gives thin negatives. What a thin negative is, is a matter of opinion, and must be settled by a comparison of the print with the impression of nature which it is wished to obtain. For many effects thin negatives are invaluable, and the student must not take the ordinary photographer’s opinion as to his negatives; but only that of an artist, for, as has been shown, low-toned prints are unrecognized by the ordinary craftsman, his aim and object is never to produce such things, these he designates by all sorts of names, whereas they may be, by their tonality, infinitely truer than his “sparkling” falsehoods. In short, it all depends on what the student wishes to express. Some of the best work done has been produced from negatives made purposely thin, which have at the same time been true in tone, and full of breadth. |Intensification.| The density of a negative can be increased by intensifying the negative; but it must not be forgotten that intensification does not, in our opinion, correct the tonality, this is a matter of great importance which has been overlooked. From this it will be seen that a negative that requires intensification is worthless for artistic purposes, and had better be destroyed at once. But as intensification may be required for some particular object, we must caution the student against the ordinary perchloride of mercury and ammonia intensifier. In many cases it acts well enough, in many others it acts unevenly and in patches, and in all cases it is not permanent. The best intensifier we know of is Dr. Eder’s, whose formula we give—
Dr. Eder’s intensifier.
| ℞ | Uranium nitrate | 15 | grs. |
| Potassium ferricyanide | 15 | grs. | |
| Water | 4 | ℥ |
Wash the plate thoroughly after fixing, so that no hyposulphite remains, and immerse in the intensifier. It works up the scale from the lower tones, which is an advantage over any other. To remove all the hyposulphite of soda it is well to treat the plate before using the intensifier, as Captain Abney directs. A drachm of a 20-vol. solution of peroxide of hydrogen should be mixed with 5 oz. of water, and the plate soaked in it for half an hour, and then washed.
Fog.
The student will find that for certain effects he may intentionally produce a slight fog over his plate, as has often been done with very good results; but if his plates are unintentionally fogged, they are ruined. Fog is due to light having had access to the plate, either during manufacture, during exposure, or during development. By developing an unexposed plate it can be proved whether it was fogged during the manufacture, as in that case the plate turns black. If the fog is caused by a leaky camera the edges of the plate, which are generally clear glass, are not fogged, for they have been hidden behind the rebate of the dark slide. Light coming through the dark slide shows itself in lines or patches, and is not general. If all these sources have been eliminated, the dark room must be suspected. This is tested by putting a plate in the slide, drawing the shutter out half way, and exposing the plate for a few minutes to the developing light. If the exposed half fogs, then the dark room is to blame.
Red fog.
We have only met with this phenomenon once, and that was in developing a uranium plate. |Green fog.| This is green by reflected light, and red by transmitted light. It is generally deposited at the corners of the plate and round the edge.
Yellow and brown fogs.
Are rarely met with, and are yellow and brown by reflected light, whereas stains are coloured only by transmitted light. The student can easily distinguish between fogs and stains in this way. We have been very successful experimentally with Captain Abney’s method of clearing off green fog. He recommends the following solution to be used after fixing:—