Bromide Paper 
ExposurE.—The most convenient light-source is an elec- 
tric incandescent lamp of comparatively low candle-power, 
not more than 16, otherwise the duration of exposure is so 
brief that serious errors may arise. It is preferable to have 
the light-source fitted: with a push button, so that the light 
is only obtained while the button is pressed. This is handier 
than the usual form of switch. The light should be located 
as nearly as possible on a line with the center of the printing 
frame, and the end of the bulb should be towards the frame. 
The bench should be marked plainly with a scale of dis- 
tances, such as a yard measure, exactly parallel to the axial 
line of the light, and the frame should always be placed 
squarely at right angles to this scale. The exposures are 
practically as the squares of the distances between the light 
and the frame; that is to say, with a given light, negative, and 
paper, if the exposure at 12 inches is 5 seconds, it will be as 
12*: 24? at 24 inches, or as 144:576, or 1:4. The thinner 
the negative, the greater should be the distance from the light. 
It is advisable not to select too short a distance, as the expo- 
sures are inconveniently short. The rule that the exposures 
are as the square of the distances is not strictly correct, for 
the light has less penetrative power at greater distances and 
will not pass through the denser parts of the negative. Slow 
papers give plucky results from flat negatives, and rapid 
papers give soft results from hard negatives. 
DEVELOPMENT.—Practically, the developers for bromide 
papers may be considered as half the strength of negative 
developers. Almost any reducing agent may be used, though 
pyro is the least suitable on account of its liability to stain 
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