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HANDBOOK OF PHOTOGRAPHY 



When the objective is lowered, the yellow-green fringe first appears, and, if the 

 objective is lowered still further, the orange-blue and the red-violet combinations 

 successively appear. It is evident that, if the objective is pushed within the focus, 

 blue-violet fringes should appear bordering the black spaces of the test plate, or, if the 

 objective is pulled without the focus, the fringes should appear yellow-green. 



^-B/ue v/'o/e/- 



Ye/low green 



Objective wi+hin +he Focus Objec+ive wi+hou+ the -focus 



Fig. 8. — Diagram of color fringes as seen with test plate and a semiapochromatic objective 



when using axial light. 



Fig. 9. 



-Diagram illustrating the formation of color fringes with semiapochromatic 

 objective and white-light axial illumination of test plate. 



When oblique light is used with the test plate and a semiapochromatic objective, 

 the upper borders of the black spaces are fringed with apple-green color and the lower 

 borders with violet, as illustrated diagrammatically in Fig. 10. If the light is directed 

 from a diametrically opposite direction, the order of colors will be reversed, the apple 

 green appearing where formerh^ the violet appeared and vice versa. The same color 

 arrangement persists regardless of whether the objective is pushed within or pulled 



