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lens, building, time and photographing

ARCHITECTURAL PHOTOGRAPHY.—In photographing architecture (where parallel, vertical, and horizontal lines are included), it is essential that a lens be used that gives the least amount of distortion. It is clear, then, that a landscape or single combination lens is unsuited for the purpose. The best results are obtained with a rectilinear lens having a focal length a little shorter than the base-line of the plate. Thus, for a 15 x 12 picture, a lens of 14 inch focus, the image would include an angle of 5o degrees. For special purposes, however, such as the photographing of a building in a confined situation, it is necessary to use a wide-angle rectilinear, but for reasons mentioned under Wide Angle this kind of lens should never be used unless • absolutely necessary.

- — The camera should be placed perfectly level, and for this purpose a spirit level fitted into the camera is very useful. When it is necessary to include the entire building, raise the sliding front of the camera. If this is insufficient, try to get on to higher ground to take the view. If this is impossible. as a last resort, to be employed only in such a case, tilt the camera. If this is done, the swing-back must be used to restore parallelism between the planes of the object and the margin lines of the focusing screen. A small stop must then be used, wise an imperfectly sharp image will be the result.

The photographing of exteriors should rarely be attempted without sunlight striking at an angle to give shadows. Choose a time when, on taking up position with the cam era, the sun is shining over the right or left shoulder. If directly behind, flat pictures are inevitable.

An ingenious contrivance for finding at what time the sun will shine upon a building from a given direction may be made from a compass and watch-dial, thus : * Place the compass over the face of the watch in such a way that the magnetic needle will point toward the numeral XII. (see Fig. 35). Then imagine a straight line passing from the centre of the dial to the centre of the building. The numeral on the dial which this line cuts will indicate the required time.

The exposure varies, of course, with the actinicity of the light and with the distance from the object. The time required naturally increases the nearer we approach. The color of the building must also be taken into consideration and is very deceptive. It is better to err on the side of over-exposure, as the masonry, especially if yellow with age, does not reflect so much light as is imagined. For photographing the interiors of buildings, see Interiors.