ever ceased to
charm him from the moment it first captivated his heart in his boyhood
days.

[Illustration: THE CAMERA CLUB]

This Department is conducted in the interest of Amateur
Photographers, and the Editor will be pleased to answer any
question on the subject so far as possible. Correspondents should
address Editor Camera Club Department.

PAPERS FOR BEGINNERS, NO. 1.

THE ACTION OF LIGHT ON THE SENSITIVE PLATE.

The process of making photographs has been made so simple by modern
science that the most of us make our picture by intuition--that sort of
sixth sense by which we know just how long to expose a plate, when to
take it from the developer, when it is fixed sufficiently, etc.,
etc.--though we can give no scientific explanation of our methods, and
know little or nothing how the chemical changes are produced which
result in the finished photograph.

It is not at all necessary to know the process of making a sensitive
plate, but it is quite necessary to know something of the action of
light on the plate in order to make a good picture. A photographic
negative is formed by the chemical action of light admitted through a
lens or even a tiny hole, into an otherwise light tight box, and
striking a glass plate, film, paper, or celluloid, coated with sensitive
silver salts. The part of the light that affects this coating is the
blue rays.

The rays of light may be separated by the prism into a band of five
different colors--red, yellow, green, blue, and violet. Three of these
colors--the red, yellow, and blue--are called the primary colors, for
any color or shade desired may be obtained by blending and mixing them
in different proportions. These three primary colors have each a
separate power. The red rays possess heating power, the yellow rays
possess illuminating power, and the blue rays chemical power. The blue
rays are called actinic, and when we speak of actinic light we mean the
blue rays which produce the chemical change in the sensitive plate. The
effect of these actinic rays may be seen in other things besides the
sensitive plates. The fading of carpets, draperies, and clothing, the
tanning or browning of the skin, etc., are due to their action.

After the sensitive plate has been exposed in the camera to the chemical
action of the blue rays, the change which has taken place is invisible
to the eye, and in this state is called the latent image, because it is
dormant or