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I sincerely believe every landscape photographer NEEDS a polarizing filter.  It’s arguably the most important filter in your camera bag, but why do I think that?

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We’ve all heard the saying from the anti-filter camp of photographers, “Why put a cheap piece of glass in front of an expensive lens.”  My reply to that is, “Don’t buy cheap filters.”  Sure you can spend about $100 on an entry level 77mm polarizer but you can also spend $350 on seemingly the same filter from a top manufacturer.  I’ve found that when I spend about $250 on a 77mm circular polarizing filter, I’m getting good value for my money.

This is related to the cost above.  You get what you pay for when you buy filters.  A low cost, poor quality filter will have increased flare (the random scattering of light inside the lens barrel) compared to a middle of the line or top quality filter.

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The possible range of settings for the frame rate depends on the currently selected pixel clock. You can select a lower  frame rate without changing the pixel clock. To set a higher frame rate, however, you need to increase the pixel clock.

An excessive pixel clock can cause delays or transmission errors. If the data is read from the sensor at a higher speed (high pixel clock), you will also need a faster transmission over the data connection. Thus, by controlling the pixel clock, you can also influence the bandwidth required for a camera.

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It reduces reflections on wet rocks, deciduous tree leaves, coniferous needles, grass, and most importantly, it reduces reflections off of water droplets in the air which we call atmospheric haze.  In simpler terms – a polarizer cuts through the haze and naturally saturates the colours in the landscape.  You can see this in the photographs I took this spring in exactly the same spot about 3 seconds apart.  You can also see some examples on Amar Athwal’s website.  Amar is another local landscape photographer here in Banff.

Remember I said that a polarizing filter uses up two stops of light?  For this reason you should remove your polarizer when shooting at night.  It really has no effect except for adding neutral density.

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Another drawback to buying an entry level, low cost, polarizing filter is that they often have a cool colour cast and disrupt the colour balance of the scene.  Once again, you can easily avoid most of this problem by buying middle to high end filters.  A middle to high end filter is carefully crafted to reduce or eliminate the shift in colour balance towards the cool side of the spectrum compared to what you will when using a lower end filter.

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The maximum possible exposure time depends on the currently selected frame rate and is preset to its reciprocal value. You can select a shorter exposure time without changing the frame rate. To set a longer exposure time, however, you need to reduce the frame rate.

I’ll discuss the pros of using a polarizing filter first followed by a few cons.  I’ve included a few photographs to demonstrate it’s proper and improper use.  You can also review some of my photographs where I almost always used one.  All of the follow points are relevant for landscape photography and to all wildlife and landscape photographers.  To learn how to use a circular polarizer properly and see example photographs please see my blog article “How to Use a Circular polarizer Correctly to Improve Your Landscape Photography“.

The cost of a good polarizing filter for autofocus lenses start at about $200 for a 77mm filter.  The image quality improvement over a cheaper polarizing filter is noticeable.  I would even go as far to say that I’d rather shoot without a polarizing filter than shoot with a less expensive, poor quality filter.

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You can see that polarizing filters have a lot of benefits in Landscape photography.  I recommend buying one and simply leaving it on the front of your lens unless you find yourself shooting in overcast light when you should probably just remove it.  I also recommend removing it if you’re using flash.

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I had a hard time deciding if this point was a pro or a con.  A polarizing filter works best at 90 degrees to the sun.  That means when you use an ultra-wide lens parts of the sky can turn deep blue to almost black while other parts of the sky at a smaller angle to the sun can be light blue.  This just looks bad in a landscape photograph.  The way I manage this is to look through the lens and turn the polarizer until I see a believable effect.  WYSIWYG as you look through the veiwfinder before you trip the shutter.  It might be a good idea to critically examine the photograph on the LCD too after you take the photograph to see if you have a realistic and believable blue sky.  When the proper amount of polarization is applied to the sky, it tends to look pretty good.

Linear polarizers.  Does anyone use these anymore?  Most modern DSLR cameras use a phase contrast focusing system and need circular polarizers in order to achieve reliable autofocusing.  Sometimes you may see linear polarizing filters on sale at some camera shops as they try to get rid of old stock.  Do not buy a linear polarizer for your autofocus camera.

The basic parameter for camera timing is the pixel clock. It determines the speed at which the sensor cells can be read out.

When you pick up a polarizing filter you’ll immediately notice that it’s dark when you look through it.  That translates into the filter using up about two stops of light.  That is, if the correct exposure for a scene is 1/1000s and f/8 without the filter on then the correct exposure with the filter on becomes 1/1000s at f/16 or 1/250s at f/8, or some variation thereof.  This can become an issue in wildlife photography where you to be use a shutter speed setting around 1/2000s to freeze the movement of your subject.

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It protects the front lens element from finger prints, scratches and other precious lens coating destroying dirt.  The acidic oils from your fingerprints on the front lens elements will dissolve the lens coating in the shape of the fingerprint.  This will permanently reduce the level of image sharpness that your lens can produce.  Also, strange flare patterns can occur when the sun invariably strikes the damaged lens coatings on the front element.  However, coatings on your polarizing filter can be damaged by fingerprints too.  It is important to wipe fingerprints off of the filter if your happen to touch the front or rear glass elements and leave a smear.  However, a circular polarizing filter is a small faction of the cost of a nice camera lens so even if it gets damaged by fingerprints you can take comfort in knowing that the “insurance” of the filter paid off by protecting the lens coatings on the more expensive lens.

The increments for setting the exposure time depend on the sensor's current timing settings (pixel clock, frame rate). The exposure time values are rounded down to the nearest valid value, if required. For this reason, the actual exposure time can deviate slightly from the exposure time you have selected.