A Manual Of Photography

302 PRACTICE OF PHOTOGRAPHY. to have any required opening in front of the camera. The whole of this screen being mounted on rollers is easily moved; there- fore the operator has it in bis power to adjust the opening, and to shut off all adventitious radiations, thus securing the effective- ness of the rays proceeding directly from the sitter, or the object to be copied. The sitter should be placed in the easiest possible position compatible with the arrange- M ment of the body as nearly as is possible in a vertical plane. This is necessary, as the parts which are nearest the glass suffer a very considerable degree of distortion and enlargement. Of course 8 great steadiness is required on the part of the sitter during the few seconds he submits to flic I operation of the photographer. It is usual to "AI6 support the head by a rest fastened to the back of the seat, as shewn in fig. 82 ; but where the person 1 can maintain a steady position without this, the H , 6 result is generally the most satisfactory, the “ rest” not unfrequently giving an air of stiffness to the / sitter. In a great number of portraits a dark and unnatural shade is thrown under the eyes : this arises from the employment of a “top light.” The / light falling vertically produces the shadow of the 82. brow over the eye, and gives a sombre character to the face. This is objectionable also, as being annoying to the sitter, who assumes in consequence a somewhat painful expression. Those who have attended to the analyses of the spectrum, included in the second division of our subject, have become aware that the radiations from al1 coloured objects are not alike. A long description would not render this so apparent as a single illustration. The Frontispiece represents, therefore, a female figure, to winch purposely a blue face lias been given, who carries on her head an earthenware vessel which has a general yellow colour, and whose dress consists of the lightest colours, yellow, red, and green ; an exact copy of a photograph taken from such a figure is placed beside it, and the result is, a very white-faced female, from the intense action of the blues, clothed in dark dress from the want of chemical action in the radiations proceeding from the gay dress of the original. Hence it is of the utmost importance, particularly to ladies, that they should be directed to avoid in their dresses, when about to sit for their portraits, such colours as would produce darks for lights, and the contrary.