|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 2. The target was constructed of clear acrylic covered with colorless,
polarization-active Mylar. (A) Unmodified photograph of the transparent target
viewed under polarized light. (B) Polarization contrast image of the target
(trans-illuminated by vertically polarized light) generated by taking two
photographs through a polarizing filter that was rotated by 90° between
exposures. Each pixel brightness is equal to
255[(Iv–Ih)/(Iv+Ih)],
where Iv and Ih are the pixel values
when the transilluminated target is viewed through a vertical and horizontal
polarizer respectively. (C) Same as in B but with wax-paper diffuser
depolarizing the light. Because the neural responses of P. clarkii to
changing e-vector depend on the rate of change
(Glantz, 2001), and possibly on
color, it is impossible to simulate how the moving target appears under each
condition. Thus B and C are probably only an approximate indication of the
contrast of the target under polarizing and non-polarizing conditions,
respectively. The bar on right shows the contrast scale.
|
