Almost Free Polarized Light Photography.

Taking a good picture of something shiny like electronics is hard. Here's an almost-free way to turn your existing or old cellphone camera into a polarized light camera.

Polarized filters have long been used to cut down reflections in photography. When combined with strongly polarized light sources, the effect can be very dramatic.

Buying high quality polarized filters for a camera and lighting gear can get expensive quickly. Luckily, the 3D movie industry had subsidised the cost of small filters via 3D glasses handed out for free at some movies.

Materials:
- A set of the "disposable" 3D glasses from the movies.
- An existing cellphone with camera.
- Tape (electrical or gaffers is ideal.)

Tools:
- Thin, flat screwdriver to dismantle 3D glasses
- Scissors and/or razor

Dismantle the 3D glasses to get the polarizing filters out. You don't care about the frames, just the thin plastic eyepiece. Be careful not to wrinkle them. If you want, you could just cut one of them out using a razor.

Eventually, you'll want two small squares of material, but it's very important to keep the orientation consistent. The polarized material is like a microscopic wood grain. It's not as important to know which way the grain runs, but it is critical that both pieces have the lines running the same direction. I did this by cutting a rectangle out of the material, then cutting that rectangle in half to get 2x squares.

NOTE: it is more important to get the cut that divides the piece in half at an exact right angle and then have these two edge touching later. Apparently, even a 1 degree misalignment of the polarization patterns will cause a blue hue. See comments from Dave.

Clean everything using eye-classes quality cleaning products (e.g. soft cloth). Hint (I find it easier to wear latex gloves to stop from resmudging as I go).

WARNING: This step not required. You should really try just covering the camera lens with a filter before removing the existing one. Doing so voids warranties, etc. I've removed filters from older cameras with no noticeable negative effect; however, each cellphone camera will be different.

OPTIONAL: I removed the existing lens filter from my old Droid Incredible because it was scratched. Also, the raised edge made it difficult to get the new filters to lay flat.

You don't have to do this step, but I've gotten much nicer results by removing it. (Later, you can also turn your camera phone into an infrared camera when you are done with this hack. That instructable coming soon).

There are 4 combinations to try. What you want is to find the DARKEST (most opaque) view when the filters are overlapped. Rotate the two squares 90 degrees to each other.

Flip one over so the back face is front.

Now rotate another 90 degrees.

The goal is to figure out what orientation has the darkest combination.

Ideally, you want the cut that separated the two halves to be touching the next step.

Once you've figured out which orientation is best, just tape one square over the camera and the other over the camera flash in this same orientation.

You should have the edges from the cut-in-half step touching and flush. This will help align the polarization "grain".

I'm not going to tell you how to tape the plastic, but you want to use some tape that won't leave behind glue and doesn't look too janky.

You want force on the flash for your digital camera.

You'll need some ambient light to help the camera focus, but you don't want too much of this unpolarized light.

I like having this secondary light source be dim and at a low angle to what I'm shooting.

If you're not getting a strong enough effect (e.g. because you happened to get cheap 3D glasses), then you can try flipping over both filters (they are circular polarized).

Or, even better, just buy high quality plastic filters for $20. Search ebay for "3D projection FILM polarizing." The optical quality of these platic filters is good enough for full-frame digital photography but are still reasonably priced. They are also linearly polarized and work better.

Finally, you will probably need to adjust the white balance of the final images. The polarizing filters tend to be a bit too blue. Google's free app Picasa is great for this type of adjustment.