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.

Step 1: Materials and Tools

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

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

Step 2: Upcycle the 3D Glasses

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).

Step 3: OPTIONAL: Remove Existing Filter From Camera Phone

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.

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).

Step 4: Figure Out the Correct Orientation for the Polarizing Filters.

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.

Step 5: Tape Filters Onto Camera

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.

Step 6: Take Pictures!

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.

Both the light source and the lens need polarizing filters for this to work. <br> <br>The reason is this: specular reflection, the shiny reflection or glare, retains the polarization of the light source. This light is almost entirely blocked with the polarization filter on the lens. <br> <br>The diffuse reflection, which is the rest of the light, takes on random polarization. Some will be blocked by the filter, but most will get through. <br> <br>This works because current 3D projectors use circularly polarized light. Think of it as left handed twist and right handed twist. The filter each projector has a linear polarizers at right angles to each other, followed by a segment that puts either right hand or left hand twist to it. <br> <br>The lenses are made the same way except light is untwisted on lens entry and then passes through the linear filter. The twist allows the lenses to work correctly even if you tilt your head to the side. <br> <br>The reason it specifically works above is the filters are reassembled backwards to their usual use. <br> <br>Leaving the flash, the light is twisted and then linearly polarized, gets reflected from the shiny bits (still linearly polarized) comes into the camera filter, which is at right angles to it and gets stopped. The rest of the light that makes it through the linear polarizer, is polarized, and then twisted, which usually makes no difference to the camera sensor. <br> <br>The blue color is from less than perfect alignment; it takes less than a degree to go from a decent black to a very dark blue.
Great information Dave! Thanks!! <br> <br>I flag it as a Featured Comment.
Ready to &quot;go pro&quot; and use this technique with a high-end digital camera? <br> <br>I recommend getting filters used for 3D movie projectors. The opitcal quality is better and the polarizing effect is stronger. <br> <br>You can get 2x small filters on ebay for $19. Search ebay for &quot;Twin 3d projection FILM DIGITAL&quot;. <br> <br>You'd use the same technique I've described here, except you'd attach one filter to an external flash or LED light lamp.
This is awesome im so doing this
Question: what's the improvement if you only polarize the lens and not the flash? Or vice versa? <br>Thanks for this idea!
I think one term used for this approach is Cross-Polarization. Here's a good article using it with 35mm cameras: <br>http://www.naturescapes.net/042004/wh0404.htm <br> <br>I haven't seen this technique used very often, but polarizing the light had a notable effect with macro photography. I assume this is because there isn't as much bounced light sources. <br> <br>A single polarizer filter over the lens is great for shooting outdoors. It will cut the glare off water and make clouds visually pop. <br>
You should only polarize the lens. That's how cameras have been doing it for years. That's not a good explanation, so I'll theorize. <br>I would think that a flash polarization would be dispersed and reflected too much to matter really. Also, luminous intensity is inversely proportional to the square of the distance the light has to travel. Having a set of polarizers on the lens guarantees that all your light gathered is passing through the filter.
I know you marked it as an optional step, but I don't think the average person should be removing the camera filter. I recommend adding a warning about breaking things, voiding the warranty, etc. I'd think it would be better to try the polarizer without the mod first and only change the camera if things didn't look so great. Phone optics may differ from brand to brand.
Excellent point. I'll update it with a strong warning.
Great first project. I would love to try this; that is, if my smart phone had a flash :(

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