10
SCIOPTICON MANUAL.
a lens, may help to correct the common impression that
these properties and a convex lens are inseparable.
THE INVESTED IMAGE.
Of the rays of light proceeding in all directions from
every point in the object B, as from all illuminated
objects, just an assortment, that is to say a pencil from
each point will enter the hole at S, just in line to fall in
reverse order upon the screen A, forming an inverted
image.
The picture results from admitting just an assortment
and excluding all the rest.
COEOS AND SHADING.
Light from each of the several parts of the object B
illuminates with its peculiar color and relative intensity
each corresponding part of the image, so that it is seen
in natural light and shade, and in natural colors. The
photographer can fix the relative shading, but ho cannot,
as yet, fix the colors.
MOTION.
If, for example, the bird moves to a higher porch, the
pencils of light will fall to a lower place on the screen,
and so any movement of the object which alters the
direction of the pencils of light, will give a reverse
movement to the image.
SIZE.
By inspecting the angle of extreme rays it will bo
seen that the imago in this case is smaller than the ob¬
ject, because it is nearer the aperture; so in all cases,
the relative size of the image depends on its relative
distance from the aperture.