Circular Polarizers

A circular polarizer is a filter placed in front of a camera lens to reduce the amount of reflected light travelling through the lens and landing on the sensor (or film) in your camera. Today, almost all polarizer filters sold are circular polarizers which work with modern auto-focus cameras.

Professional photographers often use polarizer filters to:

• remove unwanted reflections on shiny surfaces (e.g., a wind, glass coffee table, model’s glasses, etc.);
• remove glare from water, snow, beaches, etc.;
• reduce the effect of atmospheric haze in the sky area (make the sky “bluer”, enhance detail in clouds);
• increase colour saturation (by removing light reflections and glare from tree leaves or any other moderately shiny surface).

Amateur Hour

In many instances an image can be vastly improved by the careful application of a polarizing filter, and yet I rarely see amateur photographers using such filters. I guess filters fall into the category of overly complex and hard to understand. Not being a physicist, I’m not sure I completely understand how polarization works, but I know that it does. And yet, almost anyone who drives a car, skis, or plays golf knows that wearing polarized sunglasses greatly improves vision in sunny situations.

Why then, are amateur photographers not using photographic polarizer filters more often? The answer, I believe, is two-fold. One, filters seem complex, and polarizers even more so. Two, camera manufactures do not include support for filters on 90% of cameras (i.e., no point-and-shoot that I know of has threads for attaching filters). In response, I say this: one, polarizers are dead-simple to use, and if you have lenses with filter threads there is no excuse for not using a polarizer under in many outdoor situations; and two, manufacturers choose not support filters on point-and-shoots because they think you are too dumb to use them even though they know that a polarizer will be a benefit in the vast majority of images you take with their cameras, but there is a workaround (more on that in a moment).

Some Samples

For a recent trip to Argentina, I decided to take my Canon EOS M and the EF-M lenses I have (22mm f/2, and 18-55mm f3.5-5.6). I haven’t travelled with an interchangeable lens camera for a while (I love my Canon Powershot S-series cameras). However, I surmised that there might be a few situations where a polarizer would be really valuable. Unfortunately the two lenses I was taking have differing filter thread sizes (43mm and 52mm respectively). Luckily my local camera store had a 52mm mid-grade Hoya in stock for about $50CAD (a large 77mm polarizer costs about $75CAD — approximately $1CAD per millimetre).

I mostly used the polarizer in and around the northern-Argentinian town of Puerto Iguazú in the province of Misiones. Misiones is primarily tropical jungle and famous for the enormous Iguazú Falls. In town the weather pattern was blazing sun in the mornings, building clouds around noon, and torrential rain in the afternoon. This being mid-summer, the only really bearable times to be out and about were during the relatively cooler mornings and evenings. The sun set at about 7:30pm, so the window for using the polarizer was between about 9 am and 12 noon. Most places around the falls were too wet and misty to use the polarizer at all.

The blue sky, intense sun, red earth, and green forest of every imaginable hue, lent themselves perfectly to the polarizer’s strengths. Without the polarizer, the sun and blue sky are reflected on every surface. The polarizer cuts out those reflections and lets the intense colours shine through.

Two pairs of images: un-polarized on the top, polarized on the bottom. All shot with the EOS M and EF-M 18-55mm. I always shoot raw, but have not done any post processing to these samples. Click the thumbnails for larger versions.

Top: un-polarized, 1/125 s @ f/7.1, ISO 200. Bottom: polarized, 1/80 s @ f/7.1, ISO 200

Top: un-polarized, 1/125 s @ f/7.1, ISO 200. Bottom: polarized, 1/80 s @ f/7.1, ISO 200

Negatives

One downside to polarizers is the fact that they substantially reduce the amount of light entering the lens. In these samples I had to reduce the shutter speed by about 2/3 (from 1/125 to 1/80 of a second) when using the polarizer. That is not too bad actually. A difference of a whole stop is not uncommon in cheaper polarizers. In handheld situations you might find you need to increase the camera ISO to avoid motion blur.

Another downside of polarizers is the possibility of some image degradation. You are introducing a couple of pieces of glass into the light path when you use a polarizer which may cause some loss of detail, vignetting, or other nastiness. With a medium quality polarizer with coated optics this can usually be avoided. I find that the increased saturation and reduced glare more than compensate for any loss in sharpness.

Righting Wrongs

I am currently reading Don Quixote, and this valiant old gentleman (a bit witless) is all about righting wrongs. How can more people take advantage of polarizing filters in everyday casual (i.e., amateur) photography and get the better quality images they deserve? There are several options.

1. Everyone should use an interchangeable lens camera with filter threads that support polarizers. Not likely. People like the compactness and ease of use of point-and-shoots. Going even further, let’s admit that mobile (smartphone) photography rules the world.
2. Manufactures could add filter threads to there point-and-shoot cameras. On many models this would be easy to do. On some, where the lens is hidden completely behind some sort of door when the camera is off, it might be impossible. Also, I am sure that point-and-shoot lens assemblies and zoom motors are not designed to have any sort of weight hanging off the front of the lens. A polarizer, UV filter, or such shouldn’t be a problem, but a large lens hood might be.
3. Manufactures could build polarizers right into the lens of point-and-shoot cameras. No need for a 52mm piece of glass stuck to the front of the lens. A 1omm filter inside the lens assembly and controlled by a tiny motor and touch-interface would do. This would increase the cost of cameras, so it would only make sense in mid- to high-end models, but it would also be a market differentiator.
4. You can use a third-party adaptor to attach a polarizer to just about any camera. I’ve ordered a couple of 36mm MagFilter polarizers from CarrySpeed. A thin magnetic ring is attached to the front of the camera with adhesive, and the filter attaches to the ring with magnets. Looks like a slick system. It will work on my Canon PowerShot S-110 (and any S-series camera going back to the S-90). It looks like it will work on my Canon PowerShot D10 waterproof camera. (Of course I wouldn’t use it underwater or in really wet conditions, but this is also just a really rugged sports camera and I have always wanted the option to improve its shots with a polarizer.) I even measured my LOMO LC-A and it will work on there (though I haven’t shot a frame of film since 2003). A similar filter is available for iPhone (but not the iPhone 5).
5. Ugly DIY. Enough said.

Will Apple build a touch-controlled, motor driven polarizer filter into the next iPhone. Probably not. If they did, would I get rich from the idea? Even less likely. I have a theory though: the saturated processing of apps like Instagram and Hipstamatic, or the vogue of HDR, are simply the bi-products of polarizing filters not being available for a vast spectrum of cameras and photographers. And yet the optical effect of a polarizer filter is vastly superior to anything that can be done in software.

So here is my advice. Read more about polarizers and how they can help your photography. Get one for yourself. Use it. Love it.