DICTIONARY OF PHOTOGRAPHY.
A. In chemical nomenclature, a as a termination generally indicates the oxide or hydrate of an earthy or alkaline metal; as alumin-a, lithi-a, potass-a, stronti-a, or magnesi-a. Also as a termination for the names of alkaloidal organic compounds, as morphi-a, but in this latter case the syllable -ine is now often used, as morph-ine. As a prefix in scientific and technical names a signifies negation from the Greek privative prefix a; as chro-matic having relation to colour, a-chromatic not having relation to colour.
A.A. In recipes, especially those in which a Latinoid form is more- or less preserved, a.a. after the mention of several in-gredients stands for " of each one take." Thus : -
Water......... ......iooo grammes.
Hyposulphite of soda
Acetate of ammonia, a.a. ... ... ioo ,,
i per cent, gold solution ... ... 2 ..
a.a. in this use is generally considered to be an abbreviation of the Greek ava in the sense of throughout.
Abaxial. In optics, not coincident with the axis.
Aberration. In optics, aberrations (aderro, I digress), are such departures from the ideal performance of a lens or mirror as are inherent to the construction, and thus become matters of compromise rather than complete eradication. The performance of photographic lenses is more or less marred by chromatic aberration, spherical aberration, distortion, curvature of field, astigmatism, and coma. The image formed by a pinhole, used instead of a lens, although unsharp, is not affected by any one of the above aberrations, to minimise which is the chief difficulty of the constructor of lenses. Pinhole workers occasionally