The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

	Actinic                                         Actinograph - Actinometer 35 fluid ounces) of the ordinary fixing bath, as made by dissolving one part of hypo in 4 parts of water, is mixed with 50 cubic centimetres (or aboutfluid ounces) of the acid-sulphite lye, and the bath is ready for immediate use. Even after the bath has become brownish, it may be restored by a fresh addition of the acid-sulphite lye, and continues to do its work quickly, giving clear, quick printing, and brilliant negatives. An acid-sulphite bath without hyposulphite may often be used with advantage to clear such negatives as show a yellow tint or stain. A fluid ounce of the acid-sulphite lye, oroz. of crystals of bisulphite of sodium, with from 4 to 8 ozs. of water, is acidified with sufficient sulphuric acid - saya fluid drachm - to liberate sulphurous acid abundantly. In this bath the yellow negative is soaked until the stains disappear, after which it is well washed. (See Develop-ment and Developers ; Printing, also Toning.) Actinic1 applies to that portion of light which effects chemical change, in distinction to those portions which furnish light and heat. The actinic portion of the spectrum may be said to be confined to the ultra-violet, violet, indigo, blue, and green; not, as might be supposed, to that portion which appears to us to be the most powerful - viz., the yellow. But*the division is entirely arbitrary, as all depends upon the substance exposed. Actinic Focus of Lens. See Focal Length ; Chromatic Aberration; and Monocle. Actinograph - Actinometer (as above, withI draw or write; ora measure). Any instrument which mea- sures the actinism of the sun's rays. It usually consists of sensitive paper, which can be exposed to the light in small portions at a time; and the time which it takes to darken to a standard tint will be found to bear a distinct relation to the necessary exposure required for a sensitive film, whether upon glass or paper, due allowance being made for the presence of any object of importance near the foreground of picture. An actinometer can be made by any amateur by soaking a strip of gelatino-bromide paper in a 2 per cent, solution of nitrite of potash, drying the same in the dark. When dry it should be rolled up small and placed in the inside of a box which is light- 7