Area System of marking Lenses and Diaphragms
afternoon, for the west end the morning, and never in sunshine: diffused light is far superior and less likely to give rise to halation. With regard to development, thin delicate negatives are the most suitable, and the newer developing agents, amidol and metol, will be found of great value. If records and not pictures of architectural subjects are desired, then it is wise to include in the view a two-foot rule, placed in the same plane as some characteristic feature, to indicate the scale on which the object is taken ; and the plane of the plate should be parallel to the plane of the wall or surface of the building. .The fol-lowing short account of the characteristics of the various styles of English architecture may be useful: - Norman (1060 - 1100): Round topped door and window ways; short, heavy pillars and zigzag patterns. Transition (1100 - 1200): As Norman, with introduction of pointed windows. In the later examples of this style - often called Early English - (to about 1280) the windows are narrower and the pillars are clustered. Still later (to about 1380) much tracery was introduced in the windows, this being the so-called Decorated Period. The Perpendicular Period (1380 - 1547) is characterised by prevailing upright lines in windows, doorways, and often square top to windows. This developed into the Tudor Style (1550 - 1600) in which the square top is developed and carried out as a leading ornamental idea in other ways. The Jacobean Style (1603 - 1650) is very mixed; but with a considerable infusion of classical. Archi-tectural details, if in places not easily accessible, are often best photographed by means of the telephotographic lens ; the loaded tripod and camera mentioned under Animals, Photographing, being convenient, although inside a building obvious modifica-tions will suggest themselves.
Area System of marking Lenses and Diaphragms. This was proposed by Mr. George Smith to replace the existing methods of marking stops. It is not so simple and has never come into general use. The actual method, as described by the inventor, is to measure the aperture of stop in sixty-fourths of an inch. This number is squared ; the product is the exact area of the aperture in circles, each one sixty-fourth of an inch in diameter. Thus, supposing a stop aperture measured 20 sixty-fourths, 20 x 20 = 400, the last figure is struck off and the stop