This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
A grant by a government to the author of a new and useful invention for the exclusive right of exploiting that invention for a specified term of years. The law relating to United States patents, also all information with reference to the securing of a patent, may be secured by addressing the PATENT OFFICE, WASHINGTON, D. C.
(See Light, Pencil of.)
In photography pencils are used chiefly in retouching negatives. The degrees of hardness are designated by the letters B and H, an H lead being far softer than an HHHHHH. The still softer grades are designated by the letter B, a BBBB lead being softer than a B lead.
In photography a pendulum is used for counting time. The length of a pendulum whose vibration will mark off seconds of time varies according to the force of gravity in different localities. The complete to and fro beat of a 10-inch pendulum gives a full second of time. The length of the arc through which the pendulum vibrates in no way affects the result.
A question which is of vital importance to every photographer. Permanency depends, first, upon the quality of the support for the image; second, upon the purity of the chemicals used in the sensitizing emulsion; third, upon the care which has been exercised in the various manipulations necessary to make the completed picture; fourth, upon the care that has been taken to thoroughly eliminate all chemicals not necessary for the finished print. The most permanent process is the one consisting of the most stable elements, and for this reason the carbon" and platinum (platinotype) are the most permanent printing processes. If proper precautions are taken in the finishing of bromides, gaslight, as well as the various printing-out papers, their permanency is practically unquestionable.
(See Support, Permanent.)
(See Potassium Permanganate.)
(See Ferric Nitrate.)
III. Atmosphere. Solid objects, also objects located at various distances from the camera, having the effect of distance when produced on the flat surface of a photographic print. The main idea is to give such objects the same appearance in the photograph as that seen on viewing the objects themselves from the same point as that from which the photograph was taken.
An exaggerated form of perspective. It is due to various causes; the principal one, however, is the use of an extremely-wide-angle lens, which makes the objects in the view appear more remote from the camera than they actually exist. The space between near and distant objects is also exaggerated.