Photography is one of the most delightful of recreations, and whether we are interested in it for its pictorial possibilities, its value as a recording medium, or for the scientific phenomena of which it is the expression, we shall find in its study a never-failing source of pleasure. Some workers think of the results only and care little for the processes by which they are effected ; others concern themselves with the processes and the results are of secondary importance, but the real photographer, and the only one who gets his full meed of enjoyment, finds fascination in every step of the way taken to the goal of the finished print. Now, if we give the subject a moment's consideration, we shall recognise that the taking of a photograph is a marvellous phenomenon, and it is not any matter for wonderment that savage tribes should look upon a photographer as a black magician. Certainly the magician of the middle ages was one who knew a little more of the laws of nature than his fellows, and as a result of this knowledge he stood a good chance of ordeal by fire to prove that after all he was much as other men.
HOW TO TAKE A PHOTOGRAPH.
To take a photograph, it is necessary to have a camera or box into which light can only enter through an aperture at one end. This aperture may be simply a small hole, or a greater refinement is attained by passing the light through a lens. A camera or box with a hole at one end will make quite excellent photographs. Should we wish to try the experiment, it is well to get a box which will hold an ordinary photographic plate, say, the size known as 1/4 - plate, and which measures 4 1/4 x 3 1/4 inches. In the centre
THE SIMPLEST CAMERA.
of one end of the box we bore a hole, and over this place a piece of thin brass, preferably blackened, in which a hole has been made with a fine needle, say a No. 10. (a) The edges of the brass plate should be glued to the box with black paper and the box should be lined with black paper so that it is thoroughly light-tight. Now, in the " darkroom," by the light of a ruby lamp, we fit a rapid photographic plate in the end of the box facing the hole in the brass plate, close the lid and see that it is absolutely light-tight, wrapping black paper round it, if necessary, and meanwhile covering the pinhole. If we set our box on a table or stand and uncover the pinhole on a sunlit street in say,May to July, from 9 a.m. to 3 p.m.,and give an exposure of about 12 seconds,(b) we may expect to get a good picture on development, providing the sensitive plate is set about 5 inches from the pinhole. If the plate is further from the hole the time must be increased, as also it must for slow plates, or dull light, or other months of the year. It will readily be seen that such an arrangement as this simple camera is too slow for photographing moving subjects, and consequently for all practical work we use a lens. But before discarding our box and pinhole, it will be interesting to knock out the end of the box opposite the pinhole and to hold a piece of ground glass over the opening, covering the end of the box with a cloth, then, placing our head under the cloth and directing the pinhole towards a candle flame or other brilliant object, we shall see the image shown upside down on the ground glass. The reason for this is apparent. Light rays are given from all parts of the flame and they can only pass through the small hole, and so if we draw a line from the top of the flame through the pinhole it will go towards the bottom of the plate, and lines drawn from the bottom of the flame can only reach the upper part of the plate. As light travels in straight lines through any one medium, and in this case the medium is air, it will be seen that the image can only be formed in this way. If. however, we endeavour to make the hole larger, to get through more light, we shall find our image on the ground glass becomes hazy and undecided, for rays from several parts of the candle flame impinge on one spot and prevent a sharp image. To obviate this disadvantage we interpose, between the object and its image on the ground glass, something which we call a lens, to bend the rays as we want them bent, so that all the rays emanating from any one point are brought to a focus at another point on the ground glass or sensitive plate. Now, while in this article we shall not go into details as to lens construction, it will be readily surmised that it is an expensive and difficult matter to make a lens of very large size or aperture, so constructed that rays striking any part of its surface shall be correctly bent and brought exactly into focus, or in other words, so that they meet at a poi'nt on a plane surface.