This is such a fun subject to work with, and I wish I started experimenting with it earlier. I’ve tried a few things differently and I know I have more experimentation ahead of me, and I hope you enjoy the results! View large!
This freezing soap bubble is backlit by a flashlight, and the colour transitions you see are natural. I’m experimenting with a number of ways to introduce colour into these images, and I stumbled across a great idea that uses some fun research I never thought would have practical photographic uses.
The colour is the result of projected birefringence. What the heck is that? Certain materials will have a different refractive index based on angle of polarized light that hits them. I’ll save the deep science for another post (you can read about it here: en.wikipedia.org/wiki/Birefringence ), but it means that polarized light behaves strangely with certain objects. In this case, the object that I’m using is a piece of broken clear plastic from a CD case.
When polarized light (a polarizer is in front of the light source, not the camera) hits the plastic, the light will refract based on the stress patterns in the plastic. Near the injection molding points and around the edges, the colours will change as the plastic structure is less uniform. This makes for an interesting pattern of colours that you can see very easily – here’s how you can do it while you read this post:
Grab your camera, and make sure you have a polarizer on your lens. Point the camera at your LCD monitor (every LCD screen emits polarized light), and hold a plastic CD case between the camera and the monitor. Turn the camera’s polarizer until it appears darkest. At this point, you’ve cross-polarized the light and you’re only seeing the result of refraction from light that has been “shifted” by the object (CD case) so that it cannot be nullified by the cross polarization effect.
Crazy colours ensue.
This is the effect that I’ve utilized here. In front of a high-powered flashlight, I have a plastic and polarizer sandwich. Two polarizers at opposing angles are secured on either side of a piece of birefringent plastic, which translates white light into a random rainbow of colours. Slight shifts to the “filter” will create different colour combinations, with patterns similar to those found in thin film interference. This filtered light is what gives this image its colour.
The filtered light is much dimmer than the original light source, so I need to crank my ISO to get decent results… but I have a more powerful flashlight on order that should help with the light fall-off. This image has an Aqua / Purple vibe going on, but many other colours are possible simply by changing the position or angle of the filter.
See what happens when I have a few spare moments and a crazy idea?! 🙂
I work extensively on snowflakes during the winter, but frozen soap bubbles are a welcome alternative. Much of the same photographic techniques are used with both subjects, including a sense of urgency when capturing your subject. To learn more about winter macro photography, check out Sky Crystals: www.skycrystals.ca/ – it’s a great resource for this kind of work, even though it’s snowflake-focused.