234 THREE-DIMENSIONAL PHOTOGRAPHY
But consider1 If this were done, the result would not be a
giantess seated at a normal table, but would simply show a normal
human being seated at a miniature table, and miniature tables
are not astonishing.
The object which is moved is the object which will alter in size,
while all other objects remain in their natural sizes.
The question will naturally arise as to why there is any size
change. A camera lens will form an image of definite size, and
that size depends upon the distance of the object. Then how is
the size altered?
In any photograph the actual size of an image, let us say the
height of the image of a six-foot man, is definite for a given lens
and a given distance of the man from the camera.
In the above figure (3), F is the camera film, L the lens, AA’
and BB’ the limiting rays. At Mi a man’s figure just fills the field
but at M2 twice as far away the height of the image is just half
that of the film. So the image height in M2 is just half of that of
M 1. There is a direct relation between the actual size of the image
upon the film and the distance of the object from the lens.
In the figure (Fig. 4) above, the man who occupies the full
camera field at Mi, is pushed back to MP, but is increased in size
as he moves backward, so that at all times his image fills the
film. It will be seen then that the height of the image upon the