Using a Polarizer to Manipulate Birefringence

The sun in the photo below apparently frames the northern tower of the Golden Gate Bridge in a perfect circle. In fact, there are apparently three "suns" in the photo. One sun is real, two of them are optical artifacts. The fake suns, including the perfect one framing the Golden Gate tower are caused by an optical phenomenon called double refraction. Double refraction is also called birefringence.

My Three Suns, photo by Harold Davis. View this image larger.

In double refraction, each ray of light separates into two rays (the "ordinary" ray and the "extraordinary" ray) when the light heads through the lens. The extra suns are in my photo caused by the extraordinary rays. The birefringence effect is dependent on how the light is polarized.

Normally, you'd want to avoid something like double refraction in your photos (although, avoid as much as can, you'll likely see some if you shoot directly into the sun with a long lens as I did in this photo).

But a few nights ago I was feeling bored, and I knew I had more than enough photos in my files for my Golden Gate book, so I amplified the effect by adding a polarizing filter in front of my lens, and rotating the outer ring of the filter to change the direction of polarization until the subsidiary "sun" was in position.

This is the only photo in the set where I got it exactly right, so try and try again is the motto if you want to go for this effect yourself. Adding a polarizer with its infinite variety of possible settings increases by an order of magnitude the complexity of finding the right photo settings under deadline (in this case, the drop-dead event was the sun sinking beneath the horizon).

[375mm in 35mm terms, circular polarizer, 1/750 of a second at f/9 and ISO 100, tripod mounted.]