Fig. 5. Effect of conduction through still air in the pit on the ratio of image to source temperature contrast for facial pits with _i=20° and various dimensions and membrane positions. The x-axis is the thickness of the posterior chamber and indicates the position of the membrane from touching the back of the posterior chamber (thickness 0) to the center of the chamber (thickness equal to half the total thickness of the pit), as indicated by the inset drawings based on Fig. 1B. The y-axis is the temperature contrast on the pit membrane for a 1°C source temperature contrast. If conduction through the air surrounding the membrane is neglected as in prior studies, this ratio is 0.058 for pits of all sizes and configurations.