Polarization Space Photos

These photographs are beyond the normal level of lollygagging. These are *special*, meaning they required more effort. These photographs are false-color. This means that the color you see is not the actual color in the image, rather it is an indication of the polarization of the light. How is it done? I took several pictures in black-and-white with a linear polarizing filter in front of the camera at varying angles. Each angle (direction of polarization) is then mapped onto a color channel and recombined into an image. If the light is not polarized, it will pass through the filter the same amount no matter what the orientation. But, if it is polarized in some direction, one of the B/W photos will pick up more light than another, making one color stand out, rather than the shades of gray produced when all colors are of equal intensity. (Remember all colors together make white, or if some shade of gray if they're all dim). In this way polarization direction is mapped onto the different hues on the color wheel. Although experimental setup always contains some degree of error and randomness, the polarizations are mapped to hues as shown on the wheel below. If a line is drawn through the center of the circle (representing the polarization direction) the color it intersects corresponds to the hue that is seen in the photo.

How to orient the color wheel is a matter of taste. Here are two photos for comparison. The first (Red Rose) has horizontally polarized light encoded onto the red channel and vertically polarized light onto the blue channel (The latter image uses the scheme in the color wheel above). The rose appears surprisingly normal. Don't be fooled though, we could just have easily made blue the horizontal polarization color. This is what was done in the second picture (Blue Rose). As you can see, it looks identical to the preceding picture except the colors are mixed up.

Above we have a picture of a chandelier taken in the same manner. Notice how the color around the light bulb perimeter varies with the angle. This is due to (I suspect) the "Brewster filtering" by the glass in the bulb.

Coming "Soon"

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