Tips and Tricks: Cross Polarization
Welcome back to Tips and Tricks, a monthly feature where I discuss an aspect of photography. In these tutorials I have discussed the fundamentals of photography dealing with exposure and composition. I have also talked about filters and their applications in landscape photography. This month we are going to let our hair down a little bit and try something a little more on the creative side. Its time to put the concept of tack sharp, technically perfect images away and concentrate more on having fun with your camera.
We are going to be discussing a technique called cross polarization this month which is something that I have just discovered recently. Actually, I had read about it a couple of years ago, but did not have the appropriate supplies to really make it work. Thanks to a new book I have read, Camera Creative by Chris Gatcum, I have found a different way to set things up which has made this technique something that I can now do.
So, what exactly is "cross polarization" you ask? Well, simply put it is a way of bending light around imperfections in transparent, injection-molded plastic as well as tempered, heat toughened safety glass. What started as a scientific test to determine where stress areas existed has turned into a very creative form of photography. This phenomenon is called "birefringence." The test is to use a polarized light source and view the object through a polarizing filter. In essence, this technique is "cross polarization."
Bending Light
As it turns out, most photographers have a polarizing filter in their bags which is half of the equation. The other half traditionally comes in the form of a sheet of polarizing plastic or gel. However, this is rather expensive, delicate, and once the surface is damaged it becomes much less effective. This was why I had never tried this method. For those who wish to do it the traditional way, you would cover your light source with this plastic sheet and place your object in front of the now polarized light source.
In the modern age of digital photography, the computer becomes the answer to many problems in creative photography. I'm not one to rely on computers to produce my images, but in this case, I have to admit that the use of a computer makes this style of photography much easier. Don't worry, I'm not talking about post processing through software....nope, what I am suggesting is actually using your computer as your light source.
As it turns out, most modern LCD displays on computer monitors, laptops, and even flat screen televisions are a convenient source of polarized light. All of a sudden I realized that I had several options when it came to a light source and none of them required that I go out and purchase a polarizing gel. The only thing left to do was get out the camera and give it a try.
The Setup...
Here you see the basic setup that I used. I chose to use a laptop computer which was easy to position where I needed it. I covered the keyboard with a black felt cloth to keep stray light at bay and positioned my subject about where the mouse pad is. This kept it close enough to the monitor so that I didn't get the monitor edges in the frame. For objects that are not of a material to show the stress points under cross polarization, you will need to use something between the screen and the object. I have found that using the jewel case of a CD works quite well to bend the light creating the rainbow effect.
The camera setup is pretty much as you would expect. I would suggest using a tripod because of the low light and narrow aperture that will be used. Fit an appropriate lens that will achieve the focal length that you are after. I have customarily used my 180mm f/3.5L Macro lens which enables me to get in tight and close to my subject. I also fit the polarizing filter on the front of the lens (remember, this is cross polarization). All that is left now is to open up a program on the laptop that gives a blank white screen. I chose to use MS Word and a blank document. Be sure to turn the brightness all the way up.
The Exposure...
Once everything is in place you need to set your exposure. It is best to set your polarizing filter prior to placing the object between the light source and camera. Before the light starts getting "bent" you can see the polarization effects best. What you want to do is rotate the filter until you get a nearly black viewfinder. At that point, place the object or piece of plastic in the frame and watch the colors explode! As with any use of the polarizer, you can dial in the amount of polarization that you wish, but having it set to black from the beginning will ensure the most vibrant colors. You now can set the aperture to your liking, and let the shutter speed fall where it may for an accurate exposure.
It is best to turn off any extraneous lights in the room so that your only light source is the polarized light. Between this and the polarizer, your shutter speeds will be quite low. For nice crisp color as well as a clean image, I would suggest a low ISO as well, which will also slow your shutter speed. This is why I suggest that you use a tripod as exposures in the neighborhood of 1/2 a second and slower are common.
What Can I Photograph?
Rainbow Helix
As I mentioned before, the color comes from the clear plastic, or tempered glass. If your intended object is made from these materials then you will have an easy time of it. Personally, I enjoy a bit of a challenge and prefer photographing other objects with the cross polarized plastic as a background. I have found that crystal, and clear glass work well. If the object is not clear then you will be able to capture it as a silhouette against the background (remember your light source will become backlight). To overcome this, you can go for a very long exposure and do a little light painting in order to bring out the detail in the subject.
As with most creative photography, there is very little that can be done wrong. In fact, you might decide that some of your "mistakes" make for very interesting images. My first venture into this turned out less than what I expected, however, the resulting picture had a very interesting look to it. This is what happens when you don't have the light bending material between the light source and your subject. This photo also demonstrates what your viewfinder should look like when you are setting your polarizing filter.
Cool Blue
As you can see, there is a glaring absence of the rainbow colors which cross polarization typically produces. However, with a little tweaking of the white balance in Photoshop I was able to turn this "mistake" into something that I am still quite happy with.
Rainbow Abstract
With the exact same setup as above, I just included the clear plastic jewel case from a CD between the light source and the glass. The difference, as you can see, is remarkable. You can see in the background the various colors that indicate the stress points. The clear glass bends this light further adding different patterns, but with the same colors. I think that this adds a lot of visual punch.
Speaking of visual punch, I feel it necessary to say that in this type of photography its perfectly acceptable to play around with the image after capture. It is creative photography after all. I've found that white balance has a lot to do with the final colors so don't be afraid to warm and cool the image to taste. Contrast is another adjustment that really makes a difference in the intensity of the colors. My favorite tweak is cross processing (which is shown in the opening image). This mimics an old film processing technique where different chemicals are used than what are called for. It supersaturates some colors, while changing the relationships of other colors. The end results can be garish and odd, but occasionally it can be just the thing needed to make an image pop. Its worth experimenting with before you commit to a final image.
This technique earns a one star rating in the book Camera Creative for being quite easy to do. It shouldn't require any additional items than what you already have, so it come down to finding a suitable object to photograph. If you would like to try your hand at this technique, be sure and send me a link either through email or in the comment section here. I would love to see some other examples of this type of photography. I think you will find it easy and very enjoyable...the perfect thing for the colder months.
Written by Greg A. Kiser
Posted by Greg A. Kiser at 12/28/2009 7:36 PM 
Categories: Tips and Tricks,Creative Photography,Features
Tags: Photo Tutorials Painting with light Features
Categories: Tips and Tricks,Creative Photography,Features
Tags: Photo Tutorials Painting with light Features
Happy New Year Greg!
I intend to play with this technique and hope I may obtain a photograph that captures a little of the Light Fantastic!
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I only had one object that would work for this, a dandelion clock embedded in plastic.
I have posted my fantasies at
http://visualcounterpoint.com/apps/blog/
Now I will be hunting for more objects, as the weather is still bad!
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Hi Greg, I always wondered what polarization was! Seems like a fun project to do while your still pretty much stuck inside, I'll have to give this a try! Thanks!
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Do you half to use a laptop?
I would like to use studio lights.
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Great blog this will help me in my photography class...
Thanks for posting...
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