Cross-Polarized Lime

This is another entry in The Daily Post Photo Challenge: Experimental.

We have been experimenting with macro photography of readily-available fruit. One technique we wanted to try was using cross-polarized light. Generally, light scatters in all directions. A polarizer filters light so that only streams of light in parallel planes pass. Theses filters are used in photography to eliminate reflective glare and improve contrast.

Two polarizing filters can be arranged in sequence with light passing through the first filter and the camera lens behind the second. These filters can be rotated to block all (really almost all) light. If a translucent object is placed between the filters, it can scatter some of the incoming light. Different regions in the object can scatter the light to different degrees. Some of the scattered light is aligned with the second filter and is visible to the camera. Whew!

We placed a thin lime slice (a.k.a a translucent object) between the first filter illuminated by a light table and the second filter attached to the lens of a tripod-mounted camera. The first filter was mounted in a hole cut in black poster board to prevent other, non-polarized light from leaking through and reaching the camera. The filter on the lens was then rotated to maximize the contrast in the image. The following image shows the result.

A lime in cross-polarized light

The dark regions show where the light passed through the lime without having its polarization changed by scattering. The bright regions show where the polarized light was scattered as it passed through the lime and much of this scattered light aligned with the second filter mounted on the lens. This was a fun way to pass a chilly grey day at home.

This photo was taken on November 19, 2017. Specs are:

Canon 100D, ISO 100, f/8, 0.4 sec, 100 mm