If you use a polarizing filter

[dannyrich]

and it underexposes by 2 - 3 stops, surely this will do all the frame.

I dont see how that would help given that people in the shot would also be under exposed too.

Im off to buy one so im sure i'll work it our i ust dont get it.

[iNeegma]

Not sure what you mean. Polarizers stop down, not underexpose, i.e. it's like putting a piece of tilted glass in front of the lens. Since you use TTL (through-the-lens), your in-camera metering will adapt to that.

[dannyrich]

ah, maybe i misunderstood. I took it as one in the same.

So effectively it will reduce the glaring light giving me deeper colours and definition?

[iNeegma]

That's right. But please keep in mind that polarizing effect varies depending on the sun’s angle in the sky. Polarization is most effective at 90 degrees to the sun.

This means that the subject that you are shooting will display maximum polarization at right angles to the sun's position. At 180 degrees (in other words with the sun right behind you) polarization is almost non-existent.

[esmanhotto]

Originally Posted by iNeegma

That's right. But please keep in mind that polarizing effect varies depending on the sun’s angle in the sky. Polarization is most effective at 90 degrees to the sun.

This means that the subject that you are shooting will display maximum polarization at right angles to the sun's position. At 180 degrees (in other words with the sun right behind you) polarization is almost non-existent.

I've been using a polarizer in some shots and wasn't able to understand why it seemed not to work properly sometimes. I think your explanation cleared my mind...

Thanks

[kencaleno]

You will need a circular polarizer, not a linear one-both types can be circular in construction, but it's how they polarize that makes the difference . Polarizers are grey in colour, and you need to sacrifice two stops in exposure to use one. The front part of the filter can rotate to adjust the amount of polarization. The proper, intended use for these filters, is to cut glare and reduce reflections from all materials except shiny metal objects. A polarizer will help you to see through the glare of a river or a lake’s surface. Wildlife and nature photographers use polarizers sparingly, to cut the sky’s reflection on animal fur and feathers, and the land itself. To set a polarizer for such images, you point it at something earthy-brown in colour-this can be a tree bark, dirt, etc., then the front lens of the filter is rotated to give the brown dirt a dark chocolate-y colour-then it is ready to use for your nature, landscape and wildlife images. Polarizers can also deepen blue skies, making white clouds stand out, but realise that over-use can accentuate noise in blue skies. To cut glare the camera needs to be at 30 degrees to the water surface, or shop window to work 100%.To use for darkening the blue in skies, the camera needs to be around 90 degrees to the sun to have any visible effect, you just turn the front element to the shade you desire .It is a good idea to have your white balance set to cloudy, even on sunny days, as sometimes images can come out cool-looking- If you already have an 81a accessory filter for your lenses, when days are really crappy, rainy etc., attach this also to brighten your image colours. ND Grads, as the neutral density filters are usually called, come in 1,2,3,4,5,6 etc., stops, but a 2 stop is a good medium one to start with-These are used when there are more than 3 stops difference between the land/sea, and the sky-where the sky will be blown out, or the land/sea in heavy shadow. If you need to slow down your shutter speed more than your camera will allow, at the exposure you need, say to get that cotton-wool effect of waterfalls, then you will need a straightforward neutral density filter-a 2-stop will do-if you need to slow down more, just add your polarizer to slow down 2 more stops.
REgards, ken

[jdepould]

Nevermind, read it wrong.