Bryn Mawr College monographs . ISO Fig. 3. The combined effect of brightness of preexposure and surrounding fieldon the limits of the color field. In this chart are shown the apparent limits for redwith both preexposure and surrounding field respectively of white, black, and gray ofthe brightness of the color at the point of investigation. Conclusion It is quite obvious from the preceding data that repro-ducible results can not be hoped for in perimetric or campi-metric determinations of the sensitivity of the peripheralretina unless the variable effects of preexposure and surround-ing field b
Bryn Mawr College monographs . ISO Fig. 3. The combined effect of brightness of preexposure and surrounding fieldon the limits of the color field. In this chart are shown the apparent limits for redwith both preexposure and surrounding field respectively of white, black, and gray ofthe brightness of the color at the point of investigation. Conclusion It is quite obvious from the preceding data that repro-ducible results can not be hoped for in perimetric or campi-metric determinations of the sensitivity of the peripheralretina unless the variable effects of preexposure and surround-ing field be eliminated from the conditions of work. Thiscan be done completely only by making the brightness of THE LIMITS OF COLOR SENSITIVITY 393 the preexposure and surrounding field in each case the sameas that of the color employed and working under constantintensity of illumination. Among the effects of a variableintensity of illumination on the results of a perimetric orcampimetric determination the following two may be men-. \ 180 Fig. 4. The combined effect of brightness of preexposure and surfounding fieldon the limits of the color field. In this chart are shown the apparent limits for yellowwith both preexposure and surrounding field respectively of white, black, and the grayof the brightness of the color at the point of investigation. tioned. {a) When the color stimulation is given by lightreflected from pigment stimuli of a given coefficient of reflec-tion the amount of colored light obtained depends upon theintensity of light incident on the reflecting surface. And {h)a brightness match of preexposure and surrounding field withthe stimulus surface will not hold at different illuminations(the Purkinje phenomenon). 394 C. E. FERREE AND GERTRUDE RAND We have worked out in previous papers the conditionsunder which the desired standardization of intensity andcolor value of illumination and control of brightness of pre-exposure and surrounding field may be obtained in labor-
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