The Dictionary Of Photography

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

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Axis                                                             Azote, Azotate
gelatino-bromide plates, in consequence of their rapidity, the auxiliary exposure is so extremely short that indubitable proof of its advantage is hard to obtain. A method suggested, and which has certainly the merit of simplicity to recommend it, is to replace the ordinary lens cap with a flap shutter, the inside of which is a sheet of pale yellow glass, ground on one side. The shutter is so arranged that the glass and flap can be lifted together to give the true exposure ; and, when this is completed, the shutter alone is lifted, leaving the yellow glass covering the lens, and a flash as quick as possible is given through this. It is only fair to add that the benefit of an auxiliary exposure with dry plates is much disputed, and possibly because it has to be so short, or else general fog supervenes. The rationale of auxiliary exposure is that it either commences the necessary chemical action, or else adds to the action already commenced by the true exposure, and thus gives a developable image, or one which develops more easily. Auxi-liary exposure has also been suggested for printing processes, and with regard to gelatino-chloride paper there is no doubt that a preliminary exposure to white light prevents loss of detail in the high lights during the processes of toning and fixing.
Axis. The axis of a lens is the imaginary straight line which passes through the optical centre of the lens. The principal axis passes through the centre of the radius of curvature and the optical centre ; any other straight line passing through the optical centre is termed a secondary axis.
Azaline. This is a mixture of quinoline, or chinoline, red and quinoline blue, or cyanin, in the proportion of 10 parts of the former to I part of the latter dissolved in iooo parts of alcohol and, when mixed with ammonia and water, is used in ortho-chromatic photography to sensitise plates for red and yellow. The actual bath is prepared as follows: -
Azaline solution, as above......... 4 parts.
Liq. ammonia          ... ... ... ... 1 n
Alcohol         ...............      30 ..
Water..................      70 ..
Azote, Azotate. Old synonyms for nitrogen and nitrate.
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