Photography 101 – Polarizers
By Scott Bourne
If you’re new to photography, you might want to look into getting a polarizing filter for your camera lens. I recommend circular polarizers over linear polarizers. The screw on types are easiest to carry and use.
Polarizers reduce reflections and glare. Many people use them to darken skies. But be careful, it’s easy to overuse a polarizer. Don’t make the sky black!
I like to use polarizers to remove glare, which in turns lets more detail and color information show through in the picture. Look at the two photos above. The first one was made without a polarizer. Note it’s hard to read the sign. The second shot was made with a polarizer and the lettering stands out better because the glare has been removed.
Note that when using a polarizer you will effectively reduce the amount of light getting through to your camera. If you use a built – in camera meter, this will be taken into account when you make your exposure, but if you use a hand-held meter, you’ll have to factor in the light loss and manually adjust your exposure. Each filter comes with documentation stating how many stops of light are reduced by using the filter.
When buying a polarizer, if you can afford it, get one made of optical glass. While this adds to the price of the filter, it also adds to the quality. I only use B+W filters since they are made of the highest quality optical glass.
If you can’t afford optical glass, avoid store brands and look for names like Hoya, Lee, Tiffen and Sunpak.
The Filter Connection is a great place to buy filters.
(NOTE: This is not intended to be a white paper on the use of polarizing filters. It is not intended to be an exhaustive article on the subject, merely a teaser for those getting started in photography. Due to space and time considerations, I didn’t provide every possible detail herein.)
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Great tips, A polarizer is also very handy in photos which contain water that you might want to cut the reflections. Hoya are a great affordable choice.
Thanks for keeping the blog active and updated often.
I use a Hoya polarizer, which is also great for general purpose. For me, it comes especially handy when shooting real estate and want to reduce the indoor reflections made by the sun.
Note that cheaper linear polarizers are not an option for many/most modern cameras with in-body light sensors. They just won’t work. That having been said, it seems harder and harder to find them in any case, and when the clerk at QuikPhotoEquipment kiosk looks at you dumbfounded when you ask if it is circular or linear, there’s a really good chance it’s circular (still, check the box to avoid an annoying mistake).
Also, polarizers don’t just cut reflections: they *control* them. By this I mean that you can turn it one way to cut reflections off an object, then turn it 90 degrees off from that to actually drastically *enhance* the same reflections. This is a vital tool when you want building reflections, or moon reflections off water, or a certain look in a picture of a waterfall. Don’t think of the CPF as a “reflection reducer” or you’ll miss these opportunities!
Finally, the #1 use of a polarizing filter for me is sky hue and definition. In the portion of the sky 90 degrees from the sun (or so), you get a lot of reflections from particles in the atmosphere. These reflections tend to have a similar polarity, so using a CPF when shooting in that direction will filter those reflections out. The effect is similar to seen on the sign: the details of the sky (the curves and gradients of the clouds) tend to “pop” out, and the hue of the sky tends towards a deeper, more dramatic (IMHO) blue. Doesn’t work when shooting towards the sun, or directly away from it, and with a wide-angle lens you might end up with noticable sky hue changes across your picture. Again, though, think of the CPF when you are wanting to capture dramatic sky. After you’ve done it a while you’ll start to know when screwing the filter on is worth the effort before doing it!
I’ll put in a plug for Hoya’s SMC series of filters, including their polarizers. I’ve found the quality of the element and multicoatings to be excellent, placing this line at a cost/performance sweet spot. However, they do use aluminum rings which can have issues binding to the lens. A nice thing about B+W filters is their brass rings which don’t suffer this issue.
BTW, most DSLRs use a partially transparent primary mirror, with the majority of light reflected up to the pentaprism/pentamirror viewfinder area (where the exposure sensor typically sits) and the remainder hitting a secondary mirror for reflection to the autofocus module. The reflection/transmission of the primary mirror is very polarization sensitive (this is the case with any mirror when light hits it at a 45deg angle). Thus, there is a problem with linear polarizers: in addition to controlling which polarization you admit to your camera for aesthetic/photographic reasons, you’re also handing your camera light that is now linearly polarized and will interact with the primary mirror differently depending on orientation. So, you can end up changing the amount of light reaching the exposure sensor or sending a lot less light to the AF assembly than is optimum, for example. Circular polarizers simply add a quarter-wave plate to the output of a linear polarizer element, turning the linearly-polarized light into circularly-polarized light which acts as unpolarized light to anything that is sensitive to linear polarization (since it contains both directions of linear polarization in equal amounts).
Because of the way they work, there’s a way to test which kind of filter you have. Just hold it up to a mirror, with the filter plane parallel to the mirror plane. Now flip it. If the image of the filter in the mirror looks much darker in one orientation compared to the other, the filter is circular. If not, it’s linear.
“Because of the way they work, there’s a way to test which kind of filter you have. Just hold it up to a mirror, with the filter plane parallel to the mirror plane. Now flip it. If the image of the filter in the mirror looks much darker in one orientation compared to the other, the filter is circular. If not, it’s linear.”
I should make it clear that you need to look *through* the filter at its reflection in the mirror for this test to work.