How do you use a polarising filter properly and what are the potential pitfalls

Question: How do you use a polarising filter properly and what are the potential pitfalls of using this filter !?
Best Answer - Chosen by Asker:

EDIT: Be sure to buy a circular polarizer!.

A polarizer is used to darken a blue sky and to remove glare from glass, water, painted metal, snow and sand - but not from polished metal!. A polarizer also enhances colors in flowers and landscapes!.

When using the polarizer to darken the sky, have the sun on your shoulder!. Pretend you're standing on the face of a clock facing 12!. When the sun is at 9 or 3 you'll get the maximum effect!. Of course, if you're using a DSLR you'll be looking through the lens and you'll be able to see the actual effects!.

The only drawback to using a polarizer is that you'll lose 1 to 2 stops!. However, this can be useful when photographing moving water since you can use it to slow down your shutter speed!.

ex!.: You're at f11 @ 1/250 sec!. and use the polarizer!. Depending on the actual filter, your shutter speed will drop to 1/125 (1 stop) or 1/60 (2 stops)!. If shutter speed is critical, just open up to f8 (1 stop) or f5!.6 (2 stops) and your shutter speed will remain at 1/250!. You'll have to experiment a little to determine the actual light loss for your particular polarizer!.

Don't "cheap out" when buying any filter - especially a polarizer!. Stay with brands such as Heliopan, B+W, Singh-Ray, Tiffen, Hoya!.

If you'll be using it on an ultra wide angle, a thin or slim mount would be advisable to avoid any possibility of vignetting (dark corners) of your picture!.

You can also buy your polarizer to fit your biggest filter diameter (67mm, 72mm) and then buy step-up rings so you can use it on lenses with smaller filter diameters (55mm-72mm or 55mm to 67mm)!. Just don't use a smaller filter on a larger diameter (72mm to 55mm) unless there is a certain effect you're trying to create - vignetting is guaranteed!.

Every lens you own should have a Haze/UV or Skylight filter mounted to protect your front element!. Remove before using the polarizer!.Www@QuestionHome@Com

A polarizing filter depends on the direction of the light you're using!. It can cut down on reflections, or possible cut them out entirely!. It can make blue skies bluer, water clearer, and cut down on haze!. The only pitfall I can think of is that it is dark, so you will need a larger aperture or longer exposure time!.

For auto-focus lenses, you will need a circular polarizer!. For manual-focus, linear polarizers will work fine!.Www@QuestionHome@Com

Most reflected light is polarized!. Light can also be polarized by passing through the atmosphere!. A polarizing filter is used to select light polarized in one direction from light polarized in a perpendicular direction!.

But first a little bit of physics!. Light can be described as an electromagnetic wave!. There are actually two parts, an electric field and a magnetic field!. The two fields are perpendicular to each other and both are perpendicular to the direction the light is moving!. Imagine you are in a car moving down the road!. If you were a light wave and your electric field was moving side to side, you magnetic field would be moving up and down!.

The interaction between the two fields create and sustain the light wave!. By definition, the polarization is the orientation of the electric field!. In the example above, the light would be horizontally polarized!.

Now, how does this relate to photography!? There are two ways that polarizing filters are usually used in photography!. In both cases, the filter is rotated so that it blocks light polarized in one direction while letting light through that is polarized perpendicularly!. Light that is polarized at a different angle is partially blocked!.

One use of polarizing filters is to block (or allow) reflections!. If you want to show the mountains and clouds reflected in the lake, you would want to allow the reflections!. However, you might want to show rocks, fish, or a shipwreck under the water!. In this case you would want to block the reflections!. Turn the filter until you get the effect you want!. Compare that to what you would get without the filter!.

The other common use of polarizing filters is to darken the sky!. Sunlight reflecting off the atmosphere (blue sky) and clouds is polarized!. Turning the filter will change the amount of darkening!. The effect differs with the part of the sky in the photo!. Try it with sunset pictures!.

Note that a polarizing filter will always reduce the amount of light getting into your camera!. also, while it would seem like a great idea to darken the sky to make a rainbow more brilliant, it won't work!. I don't know exactly why, but you will most likely filter out your rainbow!.

The wikipedia article starts with a very scholarly discussion of polarization!. However, a little over half way down is some useful information on how it effects what we see!.

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You've already gotten lots of good info, so I'll just add this!.

Simply put, once you're framed your shot, rotate the outer ring of the CP until you see the image darken!. that's the point at which the filter is most effective!.

also, if you rotate the camera from horizontal to vertical, even if you're still pointing in the exact same direction, you'll probably need to readjust the filter!. Because, without changing anything else, the very act of rotation, of course, rotates the filter too!.

I defer to Edwin!. He's had a Polarizer a couple of years longer than I have!.Www@QuestionHome@Com

Not all digital cameras require a circular polariser, only cameras that use polarisers for sensing edges for the autofocus or exposure need them, Pentax for instance can get by perfectly well with a linear type!.

One way to tell them apart is to look through the filter into a mirror from the camera side (the side with the threads on) with a circular polariser the reflected filter will be black (opaque)!. the linear one will be grey (translucent)!.

ChrisWww@QuestionHome@Com

Put simply, from what little I know you need to use a circular polarizer not a linear polarizer, and you need to turn it carefully until you see the desired effect in your viewfinder!.

It will reduce light, so you will have to open up one or two F-stops (hope that is right)!.

Here is some more info http://digital-photography-school!.com/bl!.!.!.

EDIT: I use a Hoya!.Www@QuestionHome@Com

Very complete answer Edwin!.!.!.!.

Just want to clarify, circular polarizers are best for digital cameras correct!?Www@QuestionHome@Com

If you are not deep into Photography,why bother!.Www@QuestionHome@Com

It's best to use a circular polarizer!. Circular polarizers are sort of like the tinting on your car windows, sunglasses if you will!. They make colors more colorful!. This is why most photographers use them!. Just to exaggerate colors in their pictures!. You have to turn the little part of the circular polarizer until you see the desired effect through your camera's viewfinder!. Watch this video for reference:

http://www!.youtube!.com/watch!?v=7Vvz_d6AP!.!.!.
That's from Gordan Laing

However, you can't use a CPL all the time when you're taking photos!. Don't use them on hazy overcast days!. also, they limit the amount of light which enters the lens ( to an extent ) They are like infrared filters though, so you can still get a lot of light in your images!. So don't use CPL's on dim days

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