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Sodium Tunostate

image, effect, diffused, collodion, picture, film, sharp and soft

SODIUM TUNOSTATE ( Formula, 2H ; synonym tungstate of soda, molecular weight, 317).—Prepared by fusing wolfram with sodium carbonate. It crystallizes in rhomboidal plates soluble in water, but insoluble in alcohol. It is principally employed in the toning process.

SOFT EFFECTS.—The question whether a photograph should be sharp all over or not still remains an undecided one among photographers. Many point out that the eye can only see objects on one plane, sharp. If farther away, they appear blurred until the eye focuses itself upon them, when the objects which were sharply defined on the retina beforehand become diffused. On the other hand, scientists like Captain Abney and others declare that unsharp images are unnatural.

It is not our intention here to attempt to decide the question. While for many purposes we like to see a well-defined image, yet we cannot help admitting that soft, diffused images have won our admiration, and it is our purpose to give some of the methods employed in their manufacture.

First of all, however, it must not be imagined that any picture made unsharp will be a suc cess. Nothing is more ridiculous to see than some of the attempts at diffused images made by some photographers imitating the " naturalistic " or " impressionist " school.

The artist Fives a soft effect to a picture where he thinks it necessary to convey the impression he desires. The photographer can do the same, but he must know what he is doing, and the picture itself must be his chief guide.

Diffused images are not new by any means. Many years ago Dallmeyer constructed a doublet lens so arranged that, after focnsing, the back and front combinations could be slightly separated to give a diffused effect. These were largely employed in portraiture, but the general public preferred a sharp image, where every hair of the head was plainly visible.

A diffused image can be obtained by altering the focus during the exposure, but this method is rarely satisfactory, and the results are quite different from those which give the most pleasing effect.

Vibrating the camera during the exposure was another curious method that was recom mended. A cord was tied from the center of the camera tripod head to a heavy weight on the ground. As soon as the lens was uncapped a violin bow was drawn across the cord and a vibra tion of the whole was set up, giving a peculiar diffused effect to the image.

The interposition of a sheet of transparent celluloid or a thin plate of glass between the negative and the printing paper is the manner in which some operators obtain their diffused effects. Sometimes printing is carried half way in the ordinary manner, the glass inserted and

the picture printed out. This gives a peculiar soft effect, while the image still appears sharp.

There are various other methods of diffusing the image, many of which will readily sug gest themselves to the reader. For instance, by holding a spirit lamp beneath the lens during the exposure, a rarefaction of the air takes place and the image is thrown out of focus, as often seen on a hot day when the heat rays are ascending from the stone walks.

If an exposure be made partly with a small diaphragm and partly with the full aperture a peculiar soft effect can often be produced. A picture is obtained which gives the appearance of being neither sharp nor blurred. The small stop, of course, gives a sharp image during half the exposure and the full aperture an unsharp one owing to the spherical aberration. Mr. Charles Whiting, in the last number of the "British Journal Almanac," gives another method somewhat similar to this. The following is what he says ; " I find I can produce any degree of softness or blurring desired, and the means are simple. It is to use in the place of the ordinary diaphragm others made of cardboard with the apertures ranging from f/8 to f/16, or thereabouts, and on these are glued rather thick collodion films with apertures equivalent to about f/30. I also find the thickness of the collodion film a most important factor in giving to the diaphragm its fuzzy producing qualities. If I wish to give only a soft, pleasing effect to the picture I use a diaphragm with an opening on the cardboard of f/16, together with an opening in the collodion film of f/30, and if I wish for more fuzziness I increase the area of the disturbing element (the collodion film) by enlarging the hole in the cardboard to, say, or f/8, and keeping the hole in the collodion film the same or making it smaller. If I wish to carry the effect to an extreme limit I use a thicker film of collodion, or two films combined, on the same diaphragm, and it may also be done by using one film, but without any hole at all." A method recently adopted is to interpose between the negative and printing paper a piece of bolting cloth, a kind of muslin, which can be obtained with varying degrees of fineness.