Part 355

The paper can be bought in sheets of about 17 x 22 inches. Cut these in two, coating pieces of about 17 x 11. The sheet is fastened to a drawing board by drawing pins, one at each corner. The coating brush—of camel’s hair, but it is said that hog’s is better—is filled with the creamy mixture, which has been transferred to a saucer as more convenient, and with even strokes, first one way and then the other, drawn all over the paper. It is easier to do than to describe, but all three joints, wrist, elbow, and shoulder take part, and unless the surface of the paper is too smooth, there is really no difficulty to speak of.

By the time the whole surface has been covered the paper will have expanded to an extent that makes it necessary to remove three of the pins and tighten it, and then comes the most important and the only really difficult part of the work, the softening. The softener is held exactly as one holds the pen in writing, and the motion confined altogether to the wrist, bringing only the points of the hair in contact with the coating, more like stippling than painting.

If much of the coating has been laid on, and too much is less of an evil than too little, the softener will soon have taken up so much as to require washing. This is done at the tap, drying on a soft cloth, and repeat the operation, the strokes or touches gradually becoming lighter and lighter, till the surface is as smooth and free from markings as if it had been floated.

Just how thick the coating should be is most easily learned by experience, but as, unlike ordinary carbon, development begins from the exposed surface, it must be as deep; that is, as dark on the paper as the deepest shadow on the intended print, and it should not be deeper.

While it is true that the bichromate colloid is not sensitive while wet, the coating is best done in subdued light, indeed, generally at night. Hang the sheets to dry in the dark room.

Exposure should be made with some form of actino-meter.

Development may be conducted in various ways, and is modified according to the extent of the exposure. Float the exposed sheet on water at the ordinary temperature from the tap. The exposure should admit of complete, or nearly complete, development in that position in from 5 to 10 minutes; although it should not generally be allowed to go so far. By turning up a corner from time to time one may see how it goes, and at the suitable stage depending on what one really wants to do, the otherwise plain outcome of the negative is modified, gently withdrawn from the water, and pinned up to dry.

The modifying operation may be done at once, where the exposure has been long enough to admit it, but generally, and especially when it has been such as to admit of the best result, the image is too soft, too easily washed off to make it safe. But after having been dried and again moistened by immersion in water, the desired modification may be made with safety.

The moistened print is now placed on a sheet of glass, the lower end of which rests on the bottom of the developing tray, and supported by the left hand at a suitable angle; or, better still, in some other way so as to leave both hands free. In this position, and with water at various temperatures, camel’s-hair brushes of various sizes, and a rubber syringe, it is possible to do practically anything.

«TABLES AND SCALES:»

«Comparative Exposures of Various Subjects.»—

Seconds Open panorama, with fields and trees 1 Snow, ice, marine views 1 Panorama, with houses, etc. 2 Banks of rivers 3 Groups and portraits in open air (diffused light) 6 Underneath open trees 6 Groups under cover 10 Beneath dense trees 10 Ravines, excavations 10 Portraits in light interiors 10 Portraits taken 4 feet from a window, indoors, diffused light 30

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«TABLE SHOWING DISPLACEMENT ON GROUND GLASS OF OBJECTS IN MOTION»

By Henry L. Tolman

From the Photographic Times

Lens 6-inch Equivalent Focus, Ground Glass at Principal Focus of Lens

──────+─────────────+─────────────────+─────────+────────── Miles │ Feet │ Distance on │ Same │ Same per │ per Second. │ Ground Glass, │ with │ with Hour. │ │ in inches, with │ Object │ Object │ │ Object 30 Feet │ 60 Feet │ 120 Feet │ │ away. │ away. │ away. ──────+─────────────+─────────────────+─────────+────────── │ │ │ │ 1 │ 1 1⁠/⁠2 │ .29 │ .15 │ .073 2 │ 3 │ .59 │ .29 │ .147 3 │ 4 1⁠/⁠2 │ .88 │ .41 │ .220 4 │ 6 │ 1.17 │ .59 │ .293 5 │ 7 1⁠/⁠2 │ 1.47 │ .73 │ .367 6 │ 9 │ 1.76 │ .88 │ .440 7 │ 10 1⁠/⁠2 │ 2.05 │ 1.03 │ .513 8 │ 12 │ 2.35 │ 1.17 │ .587 9 │ 13 │ 2.64 │ 1.32 │ .660 10 │ 14 1⁠/⁠2 │ 2.93 │ 1.47 │ .733 11 │ 16 │ 3.23 │ 1.61 │ .807 12 │ 17 1⁠/⁠2 │ 3.52 │ 1.76 │ .880 13 │ 19 │ 3.81 │ 1.91 │ .953 14 │ 20 1⁠/⁠2 │ 4.11 │ 2.05 │ 1.027 15 │ 22 │ 4.40 │ 2.20 │ 1.100 20 │ 29 │ 5.87 │ 2.93 │ 1.467 25 │ 37 │ 7.33 │ 3.67 │ 1.833 30 │ 44 │ 8.80 │ 4.40 │ 2.200 35 │ 51 │ 10.27 │ 5.13 │ 2.567 40 │ 59 │ 11.73 │ 5.97 │ 2.933 ──────+─────────────+─────────────────+─────────+──────────

W. D. Kilbey, in the American Annual of Photography, gives still another table for the exposure that should be given to objects in motion.

According to his method the table is made out for a distance from the camera 100 times that of the focus of the lens; that is, for a 6-inch focus lens at 50 feet, a 7-inch at 58 feet, an 8-inch at 67 feet, a 9-inch at 75 feet, or a 12-inch at 100 feet.

Toward At Right the Angles to Camera. the Camera.

Man walking slowly, street scenes 1⁠/⁠15 sec. 1⁠/⁠45 sec. Cattle grazing 1⁠/⁠15 sec. 1⁠/⁠45 sec. Boating 1⁠/⁠20 sec. 1⁠/⁠60 sec. Man walking, children playing, etc. 1⁠/⁠40 sec. 1⁠/⁠120 sec. Pony and trap, trotting 1⁠/⁠100 sec. 1⁠/⁠300 sec. Cycling, ordinary 1⁠/⁠100 sec. 1⁠/⁠300 sec. Man running a race and jumping 1⁠/⁠150 sec. 1⁠/⁠450 sec. Cycle racing 1⁠/⁠200 sec. 1⁠/⁠600 sec. Horses galloping 1⁠/⁠200 sec. 1⁠/⁠600 sec.

If the object is twice the distance, the length of allowable exposure is doubled, and vice versa.

«To Reduce Photographs.»—When one wishes to copy a drawing or photograph he is usually at a loss to know how high the plate will be when any particular base is selected. A plan which has the merit of being simple and reliable has been in use in engravers’ offices for years.

Here are the details:

Turn the drawing face down and rule a diagonal line from the left bottom to the right top corner. Then measure from the left, on the bottom line, the width required. Rule a vertical line from that point until it meets the diagonal. Rule from that point to the left, and the resulting figure will have the exact proportions of the reduction. If the depth wanted is known, and the width is required, the former should be measured on the left upright line, carried to the diagonal, and thence to the lower horizon. The accompanying diagram explains the matter simply.

«COLOR PHOTOGRAPHY:»

«A Three-Color Process.»—Prepare 7 solutions, 4 of which are used for color screens, the remaining 3 serving as dyes for the plates.