Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . ig. 198, in which the vanishing-points are omitted. Here it will be seen that the short focus lensnot only diminishes the size of the farther treemuch more than does the longer, but it bringsit nearer laterally to the line of vision, andthrows it farther back. On the contrary, thelonger focus lens draws the distant tree furtherforward and further outward, and increases itsapparent height: effects that all photographerssee constantly taking place within their own
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . ig. 198, in which the vanishing-points are omitted. Here it will be seen that the short focus lensnot only diminishes the size of the farther treemuch more than does the longer, but it bringsit nearer laterally to the line of vision, andthrows it farther back. On the contrary, thelonger focus lens draws the distant tree furtherforward and further outward, and increases itsapparent height: effects that all photographerssee constantly taking place within their ownexperience. And if we imagine that A B, A^ B\ represent,not trees, but the nearer and farther end of abuilding seen obliquely, then the lines A B CDwill represent the side of that building as it willwill be reproduced by the shorter focus lens;A G HB as by the longer, producing the samecomparative effect as shown in Fig. 197 of thefirst part. If the lines A C, B D (Fig. 198), wereextended, they would give the vanishing-point,and so with AG, B H. An objection may be made by some readers that the height of the trees, A B, A B, is. 198 WILSONS QUARTER CENTURY IN PHOTOGRAPHY. volved in making a photographic picture. A person who attempts art shouldbe well versed not only in the principles of art, but should thoroughly under-stand the technique. And so should the photographic critic not only under- not represented upon the same scale in the figure, as the focal lengths. To explain this,it becomes necessary to say a word on apparent magnitudes. Suppose we are working with a lens of 6-inch focal length, and that the tree is 75 feetfrom the lens. This ratio of 75 : J, or 150 :1, represents the scale on which the tree willbe depicted on the ground-glass. If the tree be 50 feet high, then its height in thepicture will be feet, or 4 inches. Now, if, in Fig. 197, ^ represents the focal lengthof the lens, to with, 6 inches, A B may be taken as representing the correct height of thetree, or
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