Of all the filters available, a polarizing filter is the first one you should buy to improve your landscape photography.
So What Does It Do?
The polarizing filter one thing and one thing well - it removes reflections from non-metallic surfaces:
By eliminating the reflection of light on the tiny water droplets
present in the atmosphere the polarizer brings more saturated and
slightly darker skies.
Water and reflective surfaces
By eliminating reflections, the polarizing filter will tend to make
water and other reflective surfaces more transparent. The effect will
also vary depending on the angle to the reflective surface. If you place
your camera very low above a river, the effect will be very limited. If
you shoot from a bridge above it, the water will look totally
The polarizing filter also reduces reflection from other surfaces such
as foliage and thus makes their colors look more intense. It also tends
to make shadow areas darker.
The main side-effect of the polarizing filter is that it absorbs 1.5
stop of light. So, if you shoot at 1/180th of a second and then add the
filter, you will find yourself at 1/60th of a second. This happens
whatever the orientation for a polarizer. In low light situations, some
type of camera support, such as a tripod, will be needed.
Are There Any Pitfalls To Using One?
|I used a polarizer
for this photo of sunrise from Mt. Sinai. Note the darker tone of the
sky in the upper left corner which was about 40-45 degrees from the
sunrise (just out of frame on the right).
Natural polarisation is uneven across the sky, with the most
extreme effect when you're at 90 degrees to the sun. Using a polarizing
filter on lenses wider than 24mm will make some areas of the sky much
darker than others. Some pundits suggest not using a polarizer with
ultra-wide lenses. No way. If you like the effect, go ahead and use it.
Over-polarisation can also be a problem, particularly if you're shooting
at high altitudes, or even at sea level if the sky is clear. This can
turn the sky almost black - not a good look for many scenes.
Polarization is most effective at 90 degrees to the sun. That
means that the subject that you are shooting will display maximum
polarization at right angles to the sun's position. With the sun right
behind you (180 degrees), polarization is almost non-existent.
An old trick for visualizing the maximum angle is to turn your index
finger into a gun (like when you were a child), with your thumb pointing
upward. Make as if to shoot the sun with your finger and your thumb
will point toward where polarization is at its most extreme. Remember
though that this isn't just at one angle. Rotate your wrist through 180
degrees (if you can), because the entire circle around the sun is
Polarization filters are, by thir nature, quite thick in
comparison to other screw-on filters (after all, there are two pieces of
glass in a polarizer). When used with a very wide-angle lens (e.g. a
24mm), the edges of the filter can actually block some of the incoming
light and cause vignetting - a darkening in the corners of the photo.
To combat this, if you use wide-angle lenses a lot, you can buy a
"thin" polarizer. These are made by B+W and Heliopan, among others. The
downside is that they are even more expensive than their thicker
Digital cameras give you the opportunity to examine your results
where you stand, so if the polarization effect is too strong or weak you
can always adjust the filter and take another photo. When you're
looking through the viewfinder, actually look at all parts of the scene
(in detail) and see how the polarization filter setting is changing how
it looks. Don't just look at the "big picture".
If you take panoramic photos (i.e. several photos stitched together), then don't use a polarizing filter. Each photo will be unevenly polarized and the skies in each will be imopssible to match up.
How To Use A Polarizer
Before you start using your polarizing filter
you need to check whether or not the front element of your lens moves
when it focuses. If it doesn't you're in luck, as you can rotate the
filter at any time and the effect will stay the same if you need to
refocus. Many cheaper lenses aren't so forgiving though, and using a
polarizing filter on a lens with a rotating front element takes a little
more forethought. You'll need to set the focus before you start moving
the filter - switching to manual focus can make it easier to keep the
filter in the same position.
Whichever type of lens you have, you'll need to get used to
seeing the effect of the filter as you change the orientation. The
viewfinder can get dark with the filter in place making it hard to see
the effect. You'll find it easier to see if you move the filter slowly
and give your eye a chance to see the changes in the image. Look out for
an increase in the contrast between the blue sky and clouds, and
reflections on water disappearing.
When it comes to determining the exposure you can use the built-in metering with the filter in place.
Choosing Your Polarizing Filter
There are two types of filter to consider when choosing polarizers. The
first are screw-in filters. These are ideal if you only use one lens or
if all your lenses have the same filter thread. Hoya does a wide range
of sizes at a reasonable cost.
The other option is to buy a polarizer to fit one of the square filter systems. For small diameter lenses the Cokin 'A' or 'P' ranges are ideal. For large diameter wide-angle lenses, or medium-format cameras, the Lee filter system is so adaptable it will fit almost any lens, although the polarizing filters for Lee's 100mm system are on the pricey side.
How Does A Polarizing Filter Work?
It might help to think of it like those children's toys where
different shaped blocks have to go in the correct holes. Polarizing
filters only allow certain light waves to go through the lens, while the
other waves just won't get through. By rotating the filter, different
ranges of waves are let through.
If you have an old manual camera you can often get better results
by using a linear polarizing filter. However, these filters will
confuse the TTL metering, autofocus and white balance on modern cameras.
For this reason you'll need to use a circular polarizing filter on all
The reason for this is because semi-silvered mirrors are used to
siphon off some of the light coming though the lens. If that light is
linearly polarized it renders either the metering or the autofocus
ineffective. This means that you're going to have to buy circular
polarizers unless you're shooting with a pre-1970's camera, or a view
If you'd like a more in-depth explanation of what polarization is, pop over to this informative site. It has a Java applet that mimics a polarization filter. The page may take a bit of time to load, so be patient.