If there is one thing that photographers can agree on it's the importance of having a polarizer in your bag. Polarizers filter out reflected light off non-metallic surfaces (water, foliage, glass, etc.) and enhance color saturation. Polarizers allow us to get more information into the image at the point of capture, reducing the time we spend in front of a computer doing post production. Anything that reduces our time in front of a monitor is like chicken soup for the soul.
There are many manufacturers of polarizers but a few have separated themselves by offering top-notch performance, features, and a price tag to go along. It is the author's opinion that Singh-Ray, B+W, and Lee produce polarizers that set the standard yet to be eclipsed by any other manufacturer.
Singh-Ray offers a wide variety of specialty polarizers, each with specific qualities and uses. All are optically superior. Singh-Ray's most renowned and most recommended filter is the LB Warming Circular Polarizer. Offering all the benefits of polarization, the warming filters adds warmth to the color profile. This warming lightly boosts the yellow and reds in an image. Singh-Ray now offers the same filter in a non-warming neutral, LB Neutral Circular Polarizer. The neutral version delivers the same optical resolution but attempts to deliver more color fidelity with the actual scene. Singh-Ray's LB Color Combo is the Cadillac of landscaper polarizers. It takes the LB Warming polarizer and fuses it with Singh-Ray's popular Color Intensifier, subtly enhancing all colors. LB Color Combos are essentially two premium filters stacked and glued together and the cost reflects that!
B+W makes a wide variety of polarizers, most of which are color neutral. Their multi-coated variants are industry leading in terms of flare reduction and optical quality. (Singh-Ray does not offer coated or multi-coated filters as, in their words, they do not believe the benefits to coating outweigh the negative effects, though they do not expound on what these negative effects are.) If you intend to shoot with a light source in or near the frame consider using a B+W with "MRC" somewhere in the name, of which there are quite a few. Multi-coated filters resist flare. Non-coated filters exacerbate flare. B+W's top of the line multi-coated CPol is the XS-Pro Kasemann C Pol MRC-Nano. "XS-Pro" is B+W's premium digital thin-mount line (though the front of the filter retains a few threads - a clear advantage over Singh-Ray whose thin filters omit all front threads), "Kasemann" denotes that the filter is better sealed against the environment, and "Nano" means it's easier to clean smudges and debris from the surface.
Finally, Lee Filters' circular polarizer comes in two varieties, a 105mm screw-in and a 4"x4" square to be used within Lee's slide-in filter system. Lee has long made some of the most sought after filters in photography. Indeed, even today their filters are often on backorder for months. It's quite possible for the Lee 4x4 circular polarizer to be out of stock at B&H or Adorama for weeks at a time, as it is currently! The benefit of Lee's system is the seamless use of the popular 4"x6" graduated neutral density filters from both Singh-Ray and Lee without having to attach Lee's Foundation Kit to the front of a screw-in circular polarizer, causing vignetting much sooner in the zoom range. Lee's is an elegant system and one any landscape photographer should investigate further.
For autofocus cameras you need circular polarizers. Linear polarizers will confound your camera's AF and metering.
How do these very different polarizers affect the same image?
In comparing the tonal qualities of each filter the camera was put on a tripod and set to aperture priority to easily detect any light transmission differences (and there are some), and each polarizer was adjusted for the sky. All images are straight out of the camera with no post processing done, save what is done automatically during RAW conversion using a neutral profile in Lightroom 4.
Here is the first scene without any polarization:
You can just barely make out the presence of a small cloud to the left of the frame.
Here's the Singh-Ray LB Neutral Polarizer:
Notice the small cloud on the left now? Also note that there is more tonal detail throughout the image. Capturing this in camera means you'll have more information to work with in post.
Here's the Singh-Ray LB Warming Polarizer:
The LB Warming offers the similar tonal detail (though ever so slightly more rust is evident in the left truck's fender) but the entire image is more warm, shifted to red.
Here's the same scene with the Singh-Ray LB Color Combo:
Notice all the colors have more punch to them, if subtly so. The sky, in particular, and the red hood in the foreground are richer and more saturated. The tree line looks healthier and more vivid.
The B+W offers similar tonal qualities to the Singh-Ray LB Neutral with similarly controlled specularity in the red hood, faithful greens in the tree, if a bit less intense blue overall.
Here are the color histograms of the above images:
Without polarization the color information is choked and there isn't near as much to work with as when polarized. The color qualities of the Singh-Ray LB Neutral Polarizer are almost identical to the B+W XS-Pro. The Singh-Ray LB Color Combo shows more green (by a good amount), red while the blues are fairly consistant with the Singh-Ray LB Neutral and the B+W Kasemann. Notice the reds in the LB Warming are not as intense as with the LB Color Combo, but instead the Color Combo is more similar to the B+W, though generally more red exists with the LB Color Combo over the B+W. Exposure compensation would be required, even with polarization, to account for the intense reflectivity of the metallic surfaces in this scene in order to reduce the highlight clipping thoughout all bands. As you would expect, the Singh-Ray LB Warming has less isolated blue channel (in this image with so much bright blue away from the midtone cluster) than the others, and the Color Combo attempts to push blue back to the right despite the Color Combo's warming component.
Switching gears to something more natural, here's the Singh-Ray LB Neutral CPol:
Not a bad starting point. Colors are rich and, despite the cloudless sky giving us the full brunt of the sun's light, specularity is controlled.
Here's the Singh-Ray LB Warming CPol:
As expected there is a warmer shift most noticable at the horizon line, but evident throughout.
Next is the Singh-Ray LB Color Combo:
Straight out of the camera this filter produces the most pleasing image. Colors are all rich and vibrant from top to bottom. The saturation is simply beautiful and for many photographers this is as far as they would want to go.
Here's the B+W XS-Pro Kasemann C Pol MRC-Nano:
Similar to the first comparison, the B+W most closely resembles the Singh-Ray LB Neutral.
Finally, the Lee 4x4 Circular Polarizer:
Predictably, the neutrals have been consistantly similar and the Lee continues that trend.
Here's the detailed look at what's going on with the colors above:
Not surprisingly, the Singh-Ray Color Combo really shines with the amount of color information the file contains, especially red and blue. Notice, though, how much less color information is in the B+W file, especially green. Common complaints regarding neutral polarizers have been their tendency to shift things colder but notice the Singh-Ray LB Warming Polarizer pulling warm tones up (right) without pushing the blue down. The Singh-Ray Color Combo's color histogram also features generally less stepped gradations up and down the scale suggesting, but not proving, smoother tonal changes, though other filters do better jobs with colors individually none do all the colors as consistantly.
It's quite impressive the amount of quality color information captured in camera with the Singh-Ray Color Combo. Also impressive is the tonal fidelity between the Singh-Ray Neutral and the Lee 4x4, and to a lesser extent the B+W XS-Pro Kasemann.
Of all these filters, however, the author most relies on the Singh-Ray LB Warming Circular Polarizer. The rich warm tones are pleasing in just about every situation. When incorporating people into landscape shots the results are almost hyper-real with the LB Warming Circular Polarizer.