6. spatial bandpass filter Which is commonly used in computer vision to find visual "edges" to determine the shape of objects.

8. Vf Vout Iphoto Vf Vout Iphoto High gain inverting amp Vout drops logarithmically with Iphoto

9. Vf Vout Iphoto High gain inverting amp Vp C1 R By closing the loop, we can make this adaptive.

10. Vout Iphoto Vp If the loop is closed, we have our familiar circuit which has Vout =

11. Because the ac gain of the amplifier is very high, in practice, it is better to limit the gain using a capacitor divider. Vf Vout Iphoto High gain inverting amp Vp C1 R C2 Since Vout now does the same job of feedback through the capacitor divider,

12. Delbruck and Mead Photoreceptor