Just a few weeks ago while I was down in the Caribbean, I had the fun of testing out an iPhone 5 camera polarizing filter from Photojojo. While the clip-on filter worked -- sort of -- it had a problem with causing some vignetting of photos. Now Trygger is shipping The Camera Clip (US$39.95), which is double the price of the Photojojo unit but also does its job without the vignetting limitation.
The Camera Clip was funded on Kickstarter and is a small plastic, metal and glass device that slides onto the upper right side of a "naked" iPhone 5. It blocks the flash, but generally you won't be using a polarizing filter and flash at the same time. As mentioned in the review of the Photojojo product, polarizing filters work wonders on reducing glare from bright skies and reflective surfaces.
There's a small knurled dial that is used to rotate the filter for maximum effect. I found that dial to be easy to find even without looking. There's a pass-through on/off/sleep/wake button on top of The Camera Clip, so there's no need to pull it off to turn your iPhone off or reset it. The inside surface of The Camera Clip is nicely padded with felt to keep it from scratching your phone.
As for how it works? Well, here are a pair of images using that demonstrate the effect of a polarizing filter. To be honest with you, I think the image without the effect is more realistic, but polarizers definitely have their place in the toolkit of iPhone photographers.
With the deepest polarizing effect:
With the least polarizing effect:
The top image, taken with the filter rotated for the maximum effect, shows darker blues and more contrast between the clouds and sky. On the other hand, the lower image is much closer to what was seen with the naked eye.
My favorite places to use polarizing filters are near water, where glare and reflections from the surface are removed, and when taking pictures of sunlit snow.
The Camera Clip is available from BiteMyApple.co and can also be purchased as a case for iPhone 4/4S at $49.95.