|© Tara Craigon Photography|
Text courtesy of Jim Zuckerman, PhotoGraphic Magazine, March 2011
One of the more interesting projects I’ve explored in photography is shooting birefringent crystals. Birefringence is the splitting of a light ray by a crystal into two components that are at different velocities and are polarized at right angles to each other. What this means in terms of photography is that when light passes through the crystals, you can see rainbow colors in the unique and beautiful forms that make up the crystal.
The first step is obtaining the crystals. Common birefringent substances that will crystallize are Epsom salts and photographic fix (the type used to fix black and white prints in the darkroom).If you choose to use Epsom salts or photographic fixer, you have to dissolve the solid white chemical in water and then pour the liquid on the sheet of glass. Over several hours or even days, the water evaporates forming crystals on the glass. You won’t see any colors at all at this point.
To get the rainbow colors, you have to use two polarizing filters. A circular polarizing filter screws onto the front of the camera lens, and a second (in the form of a sheet of polarizing plastic) is placed between the sheet of glass on which the crystals have formed and the light source.
|© Tara Craigon Photography|
When a light source passes through the sheet of glass from behind, and one of the polarizers (it doesn’t matter which one) is rotated, the brilliant colors of the crystals are revealed. It’s a beautiful sight. I like to position the polarizers such that there is maximum contrast and maximum color. This is obvious when you look through the viewfinder because you will see exactly what you’ll be able to capture.
Make sure that the camera’s white balance is set correctly. I recommend using the Tungsten White Balance setting assuming you are using a tungsten light source, and you should use Daylight White Balance if using window light (you can use window light but the exposures will be long). Don’t use AWB (Auto White Balance) because the colors won’t be correct. The crystals that have formed on the glass are quite small, and to reveal the wonderful detail and color you will need a macro lens or a set of extension tubes, or both. A bellows would also work well. Macro photography requires technical discipline. This means a tripod is a must, and at the same time it’s critically important to make sure that the plane of the glass is parallel with the back of the camera (i.e. the plane of the digital sensor).
Look at the set up from the side to make sure these two planes are as parallel as possible. When taking the picture, use the mirror lock-up feature to minimize vibration, and I recommend triggering the camera with a wireless trigger, a cable release or the self-timer set to 10 seconds. In addition, make sure no one is walking around in the room in which you are shooting. When a tiny subject is magnified with macro equipment, even a subtle vibration will cause the tripod to vibrate, thus making the picture disappointingly unsharp.
With significant magnification, focus is unbelievably critical. If the sheet of glass isn’t exactly parallel with the plane of the digital sensor, even f/32 won’t give you enough depth of field. Therefore, I looked through the viewfinder and tweaked the angle of the glass in tiny increments until the crystals looked sharp to me from edge to edge. I turned the autofocus mechanism off so I could add tiny adjustments manually. In this situation, autofocus doesn’t work. This technique, and all macro photography, works best when your tripod head can lock the position of the camera firmly. If there is a tiny amount of slippage typical of inexpensive heads, you’ll be very frustrated !
Give it a try! You will be amazed with the possible results!