48 ELEMENTARY PHOTO-MICROGRAPHY. 



LAMP ADJUSTMENTS. 



To set the lamp properly, the flame is first 

 turned gradually up to its working height, and 

 put with the edge of the flame (not the flat) towards 

 the condenser. The flat side of the bull's-eye is 

 put next the flame, at its proper focal distance, 

 and with centre of lens at same height as centre of 

 flame. Having done this, the photographer's next 

 step is to look right into the lens through a pair of 



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FIG. 1 6. FIG. 17. 



neutral tint spectacles, and to raise or lower the 

 flame until the whole area is brilliantly illuminated. 

 If dark spots appear in the lens, it is moved 

 towards or from the flame to get a bright disc of 

 light. If this does not give the desired result, 

 raising or lowering the lens must be tried. When 

 the bull's-eye is too near the flame it will show dark 

 patches with bright line in the middle, as fig. 16, 

 and when too far away it will appear as fig. 17. 

 If focussed but not centred, a crescent of light 

 will show at one side of the bull's-eye. A little 

 experimenting will soon give the correct position, 

 and when once this is determined, make a mark on 



