Polarizers - Will Any Old One Do?

From left to right: we have a modern Hoya HD2 circular polarizer, an early '00s circular polarizer, and finally, a mid-'70s linear polarizer. Which one would be best for you?

  Updated Sept. 25, 2021

   If you have bought an old 35mm kit at some point (or five...or fifteen...you'll get no judgment from me ;-)), you have likely encountered a polarizing filter in among the customary packet(s) of lens tissues, bottle(s) of cleaning fluid (either unopened or completely evaporated), a blower brush that develops negative thrust, crummy 2x converter (usually described as a lens ;-)), and a gaggle of other accessories to the crime. Of all that seeming detritus, the polarizer could prove to be the most useful to you in your photographic journey. But like any tool, it can be misused, overused, and in some cases even prove detrimental to your camera's metering or focusing performance, and image quality. So how do polarizers work? How can you maximize their performance? And which type of polarizing filter will be right for you? 

  What Do Polarizers Do?

    Before being able to utilize a polarizer to best effect, a basic understanding of what they do is in order. Hopefully without falling too far down the physics of light rabbit hole ;-). Light waves ordinarily vibrate in all directions. A standard polarizing filter consists of two layers of foil applied to pieces of optical glass that can be rotated in relation to each other. Each layer is arranged like a row of "bars". When both layers are oriented with their "bars" parallel (both vertically or horizontally) to each other, the light passing through is unaffected and remains unpolarized. But when the front layer is rotated 90 degrees in relation to the rear layer, now only the light in a single plane (the vertical or horizontal component, but not both) is permitted to pass through. The basic overall effect is a reduction of glare, and thus a perceived increase in the saturation of colors (blue and green being the most noticeable). Because arrays of vertical and horizontal lines are involved, the term linear polarizer is applied to such a filter. In the process of polarization, the filter also reduces the amount of light transmitted to the film or sensor, thus simultaneously acting as a 1 - 2 stop Neutral Density (ND) filter (the amount of light being absorbed depends on the type of foil used and the degree of polarization applied by the user).

   Edwin H. Land, the founder of Polaroid, developed the first practical, cost-effective polarizing foil in the 1930s (thus the origin of the name :-)). One of its earliest applications was for sunglasses. Polarized sunglasses became very popular among pilots, drivers, and fishermen, as they eliminated glare emanating from clouds, roads, water surfaces, even the glass faces of analog instruments in both aircraft and vehicles. Land was obviously very much into photography as well, and sought to apply the principles of polarization of light in that field as well, which led to the development of the screw-in linear polarizer for lenses, among other applications. Linear polarizers for photography were so effective that they remained virtually unchanged until well into the 1960's. But as new technologies, such as beam-splitters, began to find their way into a few SLR meter designs, the limitations of the linear polarizing filter began to become apparent. Beam-splitters act as polarizers themselves and so do not play well with already-polarized light, so a modified method of polarization had to be developed in order to allow them to function as intended. Thus the circular polarizer was born. This type takes the standard two-foil linear configuration and adds a third component called a quarter-wave plate behind the linear films. This plate re-orients the linearly-polarized light into a circular pattern (thus the terminology) that permits the beam-splitter to operate normally while retaining the polarization effect for the image.  Okay, that's as much physics as I can take in one sitting ;-). But it will be enough for you to make the decision on whether you will need a circular or linear polarizer for your particular camera system. 

  Linear vs. Circular - Which Will It Be for You?

    This is not as difficult a choice as it may at first seem. The reason it comes up at all is that there are a zillion cheap used linear polarizers out there from decades of production. Circular polarizers have always been more expensive than their linear counterparts due to the added quarter-wave plate component. Nowadays, since all new ILC cameras require circular polarizers, filter manufacturers do not even bother producing good-quality linear polarizers simply because circular polarizers work on every camera type to date. You can still purchase a new linear poIarizer for much less than a top-quality circular version, but it is not a good idea because of other compromises that have been made to cut costs in the construction of such filters. The basic rule is this: if your interchangeable lens camera (ILC) utilizes a beam-splitter for metering and/or phase-detect auto focusing...you will need a circular polarizer for achieving correct exposure and/or auto focus. This includes virtually all digital ILCs. Vintage SLRs with beam-splitters include:

• Canon FT, Pellix, TL, FTb(N), F-1(N), New F-1, AL-1, T80, T90 and all Canon EOS SLRs
• Leicaflex SL & SL2, and all Leica R-Series (3-9) SLRs
• Minolta X-600 and all Minolta/Sony AF SLRs
• All Nikon AF SLRs
• Olympus OM-2s Program, OM-3(T/Ti), OM-4(T/Ti), OM-30 (OM-F), OM-40 (OM-G), and all AF SLRs 
• Pentax LX, ME F, and all AF SLRs

    Let's go back to our original scenario: you pick up a non-beam-splitter SLR with an old linear polarizer. Should you bother upgrading? Not necessarily. If it is a good-quality filter in good condition, have at it. But, what determines whether a polarizer (linear or circular) or any other filter is of good quality? Here are a few factors to think about:

• Anti-Reflective Coatings - This is the biggie. The vast majority of cheap vintage linear polarizers have no anti-reflection coatings whatsoever, which can contribute more degradation to your image than the benefits of polarization are worth. Even top-quality filter manufacturers, such as B+W and Hoya, offer polarizers with single coatings to this day at the low end of their lineups. And most vintage OEM and quality aftermarket linear polarizers were also single-coated at best (which is still far better than an uncoated cheapie). As with any other type of filter, you really should invest in quality multi-coated versions that will cause the least amount of image degradation possible. Three layers of multicoating (e.g Hoya HMC) on each filter surface will get you to about 97% light transmission (without accounting for the light loss due to the polarizing foils themselves), six or more layers (e.g Hoya Super-HMC) will bump that to 99+% (ditto). The latest top-end filters (e.g. B+W MRC & Hoya HD3) are using a 7 (anti-reflection) + 1 (Nano for toughness, water-repellence & cleaning ease) per side layer formula and they claim 99.5+% transmittance (again, not including losses due to the polarizing film). Practically speaking, about the best you can hope for is around 90% overall light transmission with a high-transmittance foil, 7 or 8-layer per side multicoated polarizer. That is a considerable improvement (about 25%) on standard foil, single-coated polarizers. 
• Polarizing Foil Used - Most traditional polarizer foils applied to filter glass absorb 1 1/2 to over 2 stops of light, with cheaper ones performing the worst in this respect. Lower-quality foils also can cause color shifts and otherwise degrade the image. High-transmittance polarizing foils that reduce absorbance to just over one stop first appeared about a decade into the 21st century. Benefits include: a brighter viewfinder, better AF performance, and a boost to your shutter speed. 
• Hardened Glass & Nano-type Coatings - In recent years, the best filter makers have adopted special hardened glass types and Nano coatings to improve the resiliency, durability, and cleaning properties of their premium filters, including circular polarizers. Do not quickly dismiss the advantages of easier cleaning and greater durability when considering the undeniable price premium of such polarizers over cheaper versions lacking such features. When having to live day-to-day, year-to-year, and even decades with your polarizer, those features outweigh the initial investment. For standard filters, even the act of cleaning itself accelerates wear and light scratches that accumulate over time, necessitating replacement sooner rather than later.

    By all means, give that old linear polarizer a whirl, but remember that technology has come a long way and good quality modern (say within the last 10-12 years) circular polarizers provide a noticeable boost in anti-reflective performance over their forebears. But drop $80 - $100 USD for just a filter when I got this whole kit for that much? Get real, man. Okay, okay, okay. Here comes a tip or two:

• BUY USED or discontinued NOS (new-old stock). You can save up to 80% that way, and end up with a lifetime polarizer for most of us enthusiasts. For the two circular polarizers in the opening picture I paid: 1) $32 USD for  the 62mm Hoya HD2 in 9/10 Used condition from B&H Photo, and 2) $26 USD for the 55mm Hoya SUPER in Open Box condition from the big auction site. I also recently obtained an NOS 72mm Hoya HD (identical construction to the HD2, except that the HD2 came with a 5-year factory warranty) for $37, also from the big auction site. Original regular prices from B&H were $90, $91, and $96 USD, respectively (all prices inflation-adjusted to 2021).
• Buy ONE polarizer in the largest filter ring size of your lens set and use step-up rings to adapt it to the rest of your lenses. 

  How to Get the Most Out of Your Polarizer

    Just like watching the image in an SLR viewfinder snap in to focus for the first time as you twist the focus ring on the lens, so watching a blue sky darken and clouds pop out dramatically as you rotate your polarizer can be intoxicating. Or observing leaves snap into the most intense green or yellow you have ever seen...or seeing paint turn into a deep pool of color on a nice car as you kill reflections with a mere twist of your thumb and forefinger...and pretty you soon you are polarizing everything... everywhere... now all your dreams are in polarized light... and you can't stand in front of a mirror to brush your teeth anymore because you can't stand any reflections anywhere... and welcome to the polarization spiral ;-). 

   Oh yeah. Been. There. Done. That. It is sooo easy to overdo it with a polarizer. But the beauty of these little gizmos is that is doesn't have to be on OFF/ON, all-or-nothing, Nigel Tufnel "but-these-go-to-eleven" proposition ;-). You have, in the tips of your fingers, the ability to dial in just the right amount of polarization for a given situation. Polarizers are like spices in cooking...they are flavor-enhancers, not the main ingredient, and are at their best when used with a dash of subtlety and a pinch of restraint. Leaving a touch of glare on those wet rocks beside a waterfall, or just a bit of reflection on that pond surface to retain a sense of mystery, or to emphasize a beautiful compound curve on a classic car's fender are just a few examples of tasteful enhancement of an image via polarization.  

    One also needs to keep in mind that polarizers have limitations. They are at their most effective when used at a 90-degree angle to the direction of your main light source (e.g. the sun), and they gradually lose effectiveness the closer to parallel that they are oriented to said light source. The wider the angle of view of your selected lens, the more a banding effect (lighter and darker strips) between adjoining sections of the image will become apparent as the lens is taking in both those perpendicular (the more pronounced "darker" bands) rays versus the ones closer to parallel to the light source (the polarizer is less effective here, producing "lighter" bands and thus less glare reduction). This effect can be used creatively but more often than not serves as a distraction in the final image.

  So, What's It Going to Be?

    Ask yourself:

1. Does my current camera use a beam-splitter for metering and/or AF? If not, is there a chance that I will ever end up with such a camera? (Remember that almost every interchangeable lens AF camera introduced since 1985 and a decent number of MF bodies before that use beam-splitters.)
2. Am I prepared to accept a loss of image quality due to using an uncoated (major loss) or single-coated vintage linear polarizer (smaller loss)?

    If you answered "No" to #1 and "Yes" to #2, go ahead and use any old linear polarizer. Otherwise, get thee to a quality multicoated circular polarizer and never have to think about it again. See, that wasn't so hard, was it? :-)

   Modern, top-of-the-line B+W, Hoya, and Marumi (among others) circular polarizers offer the most bang for your buck versus boutique (Singh-Ray, etc.) or OEM (e.g. Canon, Nikon, Zeiss) manufacturers, offering excellent quality for less money. They all have some version of high-transmission foils, hardened glass and multicoatings, and easy-to-clean surfaces. You can pick up a top-quality used or discontinued NOS copy for less than half the price of a new mid-grade version in their respective lineups. A polarizer can easily outlast a number of bodies and is brand-agnostic as far as fitment goes if you ever decide to switch systems. It is also one of the last filter types that has not been successfully cloned for use in the digital darkroom as of yet. That makes it an important part of many a photog's kit today and one that will reward the care you take in selecting it for years to come :-).  

  References:

    Polarizer @ https://en.wikipedia.org/wiki/Polarizer
​    Understanding Polarizing Filters @ https://ascmag.com/blog
    How Circular Polarizers Work @ https://hoyafilterusa.com/pages
    The Physics Behind Polarization @ https://schneiderkreuznach.com
    Polarizer @ https://schneiderkreuznach.com/en/photo-optics/b-w-filters