Capturing Colors Unseen: A Simple Tutorial on Cross Polarization Photography

Cross polarization transforms images of a variety of clear subjects into rainbow, fluorescent works of art with equipment that you probably already have. Learn the easy process behind this clever optical technique to create some masterpieces of your own.

There is something truly magical about cross polarization. The first time trying this technique reminded me of the first time seeing an image develop in the darkroom. It is hard to comprehend how something so beautiful can result from such a mundane process.

I have shown the below image to many people over the years and asked them to guess what the subject is. Most will answer that it is a crystal. However, this is a crunched-up piece of cellophane tape! The ability to take something so unremarkable and turn it into an attractive photographic subject started a short series where I experimented with a wide variety of subjects to create some fine art pieces.

In the next image, I attempted to visualize how music makes me feel, by letting cross polarization tell the tale of the enjoyable emotional journey experienced by listening to some of your favorite songs. Yes, these are some of my favorite songs.

In 2021, I tackled my frustrations surrounding self-isolation boredom by turning my lens on COVID testing kits in order to highlight the amount of single-use plastic that was being generated in response to the pandemic. Cross polarization was a tool for storytelling in this instance. What can cross polarization be for you?

The Physics Behind the Art

I'm a firm believer that you should research the theory or the science before trying something out. You will have heard of polarized light and polarizing filters. This may be through your journey through photography or from something as widely known as sunglasses with a polarized coating to help minimize glare from light-reflecting surfaces such as water, glass, or snow, helping to protect your eyes from UV rays. A polarizer is an optical filter that works by blocking all incident light waves but those in a specific plane of oscillation, in line with the polarizing filter. The resulting effect of this is minimized reflections from specular surfaces. Cross polarization takes this one step further, by taking two linear polarizers – one at the light source and one between the subject and the lens, and rotating each polarizer opposite to one another to cause further light extinction. which causes the remaining light to split in the visible spectrum. This all sounds very complex, but the rest is easy.

Scientific Applications of Cross Polarization

Cross polarization, also referred to as photoelasticity, not only results in aesthetically pleasing images, but this technique is also extremely useful across many areas of science, manufacturing quality assurance, and medicine. 

Macro and Micro Photography

Cross polarization can be used in macro photography with extremely small subjects, bringing out those fantastic colors on subjects such as insect wings and other biological objects. Small details can be revealed in hard plastic and acrylic objects. Going smaller with micro photography, cross polarization can visualize minuscule creatures in bodies of water and help to colorfully visualize crystallized structures, cell membranes, and chemical compounds normally invisible to the naked eye.

Forensic and Medical Photography

Cross polarization is utilized in forensic investigations to capture detailed images without reflections from shiny surfaces, ensuring accurate documentation of evidence. This process is also useful in dental photography; The surface of the tooth is covered in shiny enamel, and dentists utilize cross polarized light in order to achieve an unobstructed view of the surface of the tooth.

Manufacturing

When certain materials, like plastics or glass, are subjected to stress, they exhibit birefringence, meaning they split light into two perpendicular components. Cross polarization allows manufacturers to analyze stress patterns during the design and prototype process. This is crucial for ensuring the quality and reliability of the final product. By studying stress distribution, manufacturers can consider factors such as load-bearing capabilities and durability.

The manufacturing application of cross polarization is what we are going to be working with in this tutorial. Transparent materials such as hard plastics are some of the best subjects for showing the technique and are what I usually photograph when experimenting with cross polarization.

Step-by-Step Guide

Materials Needed

• Any camera with manual control 
• Polarizing filter for your camera lens. I prefer to use a Circular Polarizing Filter (CPL).
• Polarized light source
• A sturdy tripod (optional but recommended for stability)
• Cheap clear plastic/acrylic objects

Set Up Your Shooting Space

Firstly, you will need a polarized light source, which can be expensive at most usable sizes. Luckily, LCD screens contain polarized film, so you will find that your laptop, iPad, or TV screen can act as your light source. I am going to demonstrate by using a 2020 MacBook Pro with a sheet of black paper under a sheet of glass on top of the keyboard to create a reflective surface with which to place my plastics and other objects. To turn the MacBook Pro into a light source, simply play a 10 Hour White Screen video on YouTube, oreate a white JPEG in Photoshop, or leave a blank Word document open.

Next, attach a polarizing filter to your camera lens. If using a circular polarizing filter, you may need to rotate the filter to find the desired polarization angle later in the process. Placing your camera on a tripod is useful for any still life shoot, especially so here, as you will want to adjust your filter and adjust your objects for best positioning.

Adjust your camera settings as necessary in manual mode to have control over the exposure. Start with a low ISO setting to minimize noise. Choose a narrower aperture, f/8 or higher, for appropriate depth of field. Adjust the shutter speed to achieve the desired exposure, keeping in mind that longer exposure times may be necessary in low-light conditions. You are now ready to shoot! You should already be able to see the vibrant colors revealed. However, you should continue to tweak your camera settings for optimal results until satisfied.

Focus on the plastic objects and rotate the circular polarizing filter on your camera lens while observing the live view or view through the viewfinder. You'll notice changes in reflections and color intensity. The background may change from pure white to purple or even black, depending on the quality and position of the polarizing filters used. Find the position where the reflections are minimized and the rainbow colors of the plastic objects become more pronounced.

Try this technique for yourselves! This is an extremely accessible technique, and everyone will already own something at home which will look great illuminated with the cross polarization technique. Follow the step-by-step instructions and share your results in the comments below. What object worked best?