It is occasionally worth while to preserve the actual clouds in the landscape which we are photographing. A sky shade-shutter will give a much shorter exposure to the sky than to the foreground; good results have also been produced with the graded light filter in spite of the severe criticism attending its introduction. Some workers tilt the dish during the latter part of development in such a way that chemical action is retarded in the upper part of the plate. But all these contrivances are only applicable to seascapes, marsh land, or open prairie, where the horizon line is not broken up by trees or buildings. The best plan of all is to expose the plate in the usual manner, and then, without shifting the camera, give a second plate one-fourth the exposure for the clouds. Both plates will be in the same register, so that the printing in of the clouds will present no difficulty when the features of the landscape have been blocked out.
Hartfield. Natural Clouds Of Negative.
Most of the so-called "moonlight pictures" are taken by a very rapid exposure to the setting sun when surrounded with clouds. In mountain scenery, or with the sea or a lake in the foreground the illusion is often very skilfully accomplished. Genuine moonlight pictures require a long exposure half an hour and upwards. The luminary herself must not be attempted - that is as part of a landscape. During the period of exposure she will have traversed a considerable part of the plate and her path will be represented by a broad white band.
Street scenes after dark may easily be taken on a backed orthochromatic or panchromatic plate and, if lighted by arc lamps, the exposure will not much exceed 2 minutes at f/8; incandescent gas may require as much as 10 minutes. Figures must be put in afterwards, if desirable at all. The most successful efforts of this kind, however, are obtained by focussing and giving partial exposure during the day time, but not while the sun is shining, or the shadows will spoil the effect. When the lamps are lit a further exposure may be given for, say, two minutes.
For flashlight outdoor pictures the following mixture may be tried, but it must not be used indoors as the fumes are acrid and poisonous:
Magnesium powder................................................ 30 gr.
Chlorate of Potash......45 gr.
Sulphide of Antimony .....10 gr.
The chlorate of potash must be ground to a powder before mixing; it explodes on friction with other substances in a mortar. Keep carefully in a dry place, and ignite with a long taper at a distance of six feet from the camera or any other person.
The camera must be focussed by scale, at infinity. For sheet lightning the centre of the lens will be pointed at near the horizon with the camera level, as the effect to be aimed at is an illuminated landscape. For forked lightning point the camera upwards in the direction of the storm, including only just enough ground (the top of trees or roof of buildings) to show which is the top of the picture. Remove the cap just before the flash is expected; a minute too soon is of no consequence, but cover the lens directly the flash is over to prevent fogging by any afterflash.
Fast flowing streams usually require a very rapid exposure. Still water, unless there are good shadows or knots of reed, either appears as a white patch or muddy and dull. We have found it a good plan to create ripples with a stone upon the surface of the pond just before exposing.
The yellow screen is of no service whatever for these subjects wherein form, light, and shade are the chief characteristics. The ordinary maxim, "Expose for the shadows and let the high lights take care of themselves," will not answer above the snow line. According to Mr. Donald M'Leish, who in this class of work has been eminently successful, the contrasts are too enormous. The high lights require much more attention than is usual, and we must rely upon after-treatment for bringing out detail in the shadows. A comparatively small stop should be used. For ordinary winter snow scenes, however, when there are dark tree trunks or cottages in the foreground, a longer exposure may be tried. The best effects are often obtainable towards evening if the weather is not too misty. Trees and shrubs covered with hoar frost must have extremely short exposures; and if the ground is covered with snow the lack of contrast in the distant background will tend to ruin the result. Sometimes it is possible to get the frosted bough against a leaden coloured sky. In fact a "London Particular" is the great opportunity for the seeker after hoarfrost pictures, if he can choose his moment when the mist has begun to lift.
It is worthy of remark that Dr. C. Atkin Swan, unlike most Alpine workers, finds that as a rule his exposures in the higher altitudes are very little shorter than those at sea-level; and he employs a yellow light filter of low multiplying factor.
There is considerable variety of opinion as to the speed of the plate suitable for landscape work, chiefly because it has only been of recent years that plates combining high speed with the other qualities desired have been easy to obtain. Comparing various makers, we find some labelling a plate "landscape" which is only marked as of rapidity 40 on the Hurter and Driffield scale. Others recommended for the purpose by their manufacturers vary from 100-200. What we need is a plate giving a considerable amount of gradation and latitude, with medium rapidity. Very seldom in the course of the year does a day occur when the air is quite still. At least there will be a light breeze stirring the foliage, and prolonged exposures are undesirable. Beginners may be content with a plate marked at rapidity 100-125, and then, when they graduate in the use of the yellow screen, adopt the isochromatic high-speed types, which can be used for short exposures almost throughout the year. We would not discourage the learner who cares to practise with the slow photo-mechanical plate which will allow of lens caps exposures with a large stop, and can be manipulated in the dark room under yellow light. He will then tread in the steps of his fathers, with a plate capable of giving almost the same effects as the old wet plate.
In photographs of the interior of buildings a window facing the camera is often found to be surrounded by a misty white fog which obscures its form, sometimes rendering its details invisible. This phenomenon is termed halation, and is caused by the bright rays of light reflected upon the sensitive film from the back of the dark slide, after passing through the glass support. In certain conditions of light, halation will occur also in outdoor pictures, especially where trees and roofs stand out in sharp contrast against the sky. To avoid this disfigurement the dark slides must be packed with cartridge paper stained a dead black with Stephens' Ebony Stain, or better still the plates may be "backed." The makers supply most brands ready backed at a slight extra charge, and some receipts for backing will be found amongst our miscellaneous formulae.
J. Craig Annan.