Polarizing filter

Polarising filters change the way that your camera sees and treats light. Particularly – when using one you’ll notice a change in how your camera sees reflections and glare. As a result it also has the ability to change the vibrancy of some colors in shots.

Without a polarising filter

With a polarising filter

Water – When shooting a picture of water adjusting your polarising filter will mean you see into the water differently, cutting out glare and even changing the colour of the water. For example when I was snorkelling off a boat off the coast of Indonesia a few years ago I took a series of photos (on my film camera) using a polarising filter that made the water look crystal clear and a bright blue color. Without the filter the shots had nowhere near the same impact with a big reflection being picked up off the top of the water and a more murky color. 

Sky – Similarly, the color of sky can change remarkably using a polarising filter. Rotating the filter you’ll see a blue sky change from a light pale blue color to a vibrant and deep blue color (depending upon where the sun is). A polarising filter can cut out a lot of the smoggy haze that is often in city shots. 

Color – Polarizing filters cut down the reflection that many objects have (even those that you might not think reflect at all). This makes the colors of some of these objects more vibrant. For example out in the garden you might notice foliage on trees looking greener than you would get without the filter. 

Other Reflections – Shooting through glass can be a real challenge at times and using a polarising filter can definitely assist in cutting down distracting reflections or glare. Similarly photographing shiny objects (like a new car for instance) with a polarising filter will change the way reflections are treated.

Polarizers Change Exposure

One factor to consider with polarising filters is that they change the exposure needed for a shot. When you see a polarising filter you’ll notice that it looks quite a lot like a sunglasses lens. The filter is dark and works by cutting our some of the aspects of light (similarly to sunglasses). As a result less light gets through to your image sensor and you’ll need to either use longer shutter speeds, a larger aperture or to beef up your ISO setting to account for this. The difference that you’ll need to account for is 1-2 stops. It’s for this reason that you won’t want to use a polarising filter at night.

Using a Polarizing Filter
These filters are easy to use. Most of you will use a circular polarizing filter which allows you to adjust how it impacts your shots but simply rotating the front element of the filter. As you do this you’ll notice that colors and reflections in your shot change. Once you've got it to a point that you like simply take the shot.

For the greatest impact try to keep the sun at 90° to you (ie to your side – not at your back and not shooting into the sun). This will help your polarizer to have the greatest effect.

Be aware that shooting in low light, overcast days or at night with a polarizer is not advisable – it’s like wearing sunglasses indoors and will cut down the amount of light getting through to your image sensor.

Varied Results

The extent that polarising filters work varies from situation to situation (often dependant upon the amount of sunlight) so it won’t have a massive impact in all situations – but in some (especially bright sunny days) the impact can be quite staggering.

References:

http://digital-photography-school.com/how-to-use-and-buy-polarizing-filters

http://www.cambridgeincolour.com/tutorials/polarizing-filters.htm

My attempt

I had a polarising filter booked out so I thought I'd test it out. Unfortunately it hadn't been bright enough in the day to make use of it so I thought I'd test its uses for managing exposure. There was a full moon so my thoughts were that I'd be able to capture a nice exposure of the bright moon without a tripod if I used a filter to limit the amount of light entering the lens.

Here's a few I managed to get with a high ISO. The filter alone wasn't really enough to get satisfactory shots. With the use of a tripod, I should have used the smallest aperture available with a longer exposure which would have allowed me to use a much lower ISO resulting in far less noise.

Next time I'll book out a bigger lens (hopefully the 500mm) and tripod to achieve much better results.

Here's a few tests I got showing the element inside a light bulb with the use of the filter, a UV filter might have been better for this purpose but I found it interesting nonetheless: