Need help on circular polarizer

[eng_keow]

I have been told that the use of a circular polarizer will help enhance the colors in landscape photography. I may be wrong...
So as usual...BUY, BUY, BUY... I got myself a cir polarizer. Read the instructions in the pamphlet which says - look thru the lens and adjust accordingly... which I see no difference when I did that. Took out the cir polarizer and held it to the light and turned the thing round and round but still did not find any difference....Please help. What should I be doing??

Thanks in advance...

[glyuen]

this might help

http://www.schneideroptics.com/info/...ation_filters/

[student]

a circular polariser does three things

1 It reduces the amount of light reaching the light sensors (CCD/CMOS/film)

2 It reduces glare

3 It makes the blue shy more blue.

(1) is simple. You should be able to see it straightaway

(2) Take you CP, go to any shop where there is a glass and look through the blass. You should see a lot of reflection. Now put the circular polariser up and look through it and turn the outer ring. At some point the glare should disappear or reduce. Or you can take the CP to a pond. Again you will see glare. Do the same thing. Whether you prefer the pond to have glare or not is entirely your taste

(3) to see the effect of CP on the blue sky, the sun must be frm your side. Not from behind you or in front of you. It will not work. There is a mathematics to this which I will not elaborate. But look at the blue sky with the sun to your right or left, and then turn the outer ring. You should see the blue sky getting more blue.

[eng_keow]

Thanks for the link. Gave me more details regards regarding how it works but still not sure how to turn it so that my pix will look good. Cheers!

[eng_keow]

Hey, that is much clearer. I shall try that later. Cheers

[espn]

It's ok.. some CPLs will show you nothing no matter how you turn, however, yes they do cut off glare and reflection

The basic usage recommended is to shoot 90 degrees from where the sun's light is coming from

[eng_keow]

BTW, does a neutral density filter act the same way as a circular polarizer?

Someone mentioned to me that I should use a gradient ND filter instead of CP.

Is that true?

[espn]

ND filter cuts off light, good for motion shots like waterfall shots, making the water smooth and silky kind of feel.

Circular Polariser increases the saturation and cuts off excessive glare from reflective surfaces. Gradient ND filter cuts off light from the one side to the other (thus the name gradient) where you turn it.

In short circular polariser should not be cutting off light unlike ND filters, however since it's a filter, there would be some light loss somehow, it's just how much light loss.

[eng_keow]

very clear and concise. Thanks.

[student]

Originally Posted by espn ND filter cuts off light, good for motion shots like waterfall shots, making the water smooth and silky kind of feel. Circular Polariser increases the saturation and cuts off excessive glare from reflective surfaces. Gradient ND filter cuts off light from the one side to the other (thus the name gradient) where you turn it. In short circular polariser should not be cutting off light unlike ND filters, however since it's a filter, there would be some light loss somehow, it's just how much light loss.

I am afraid I have to disagree.

CP WILL cut off light - period. As much as 2 stops. And yes, you can use it like a ND filter (note: NOT a Graduated ND filter)

But it is obviously NOT a gradient/graduated ND filter which only cut off light from part of the image. Example, if you are taking a picture where if you expose the foreground appropriately, the sky will be blown out, because the contrast is too high. One way to solve this is to put a Graduated neutral density filter to reduce the light from the sky, allowing details and saturaion to be better seen in the sky. Using a CP in such a circumstance is inappropriate because the contrast difference will remain the same.

[student]

Originally Posted by espn It's ok.. some CPLs will show you nothing no matter how you turn, however, yes they do cut off glare and reflection The basic usage recommended is to shoot 90 degrees from where the sun's light is coming from

I don't agree. The reason why CP appears not to work is because one do not use it properly.

[student]

Originally Posted by eng_keow BTW, does a neutral density filter act the same way as a circular polarizer? Someone mentioned to me that I should use a gradient ND filter instead of CP. Is that true?

They are all different.

ND only reduces light. Stop. Graduated ND reduces light from part of the scene.

[DarkForce]

Hi Eng Keow,

The rest have already give quite a good advise on the use of CP under the Sun (90 degree). Just want to point out beside the Sun, you can use it on reflection too.

When it comes to reflections, the polarizing filter works best on light that passes through the filter at an optimal angle of 30 to 40 degrees from the reflection surface

http://www.glennwong.per.sg/photos/p...polarizers.htm

[espn]

Originally Posted by student I am afraid I have to disagree. CP WILL cut off light - period. As much as 2 stops. And yes, you can use it like a ND filter (note: NOT a Graduated ND filter) But it is obviously NOT a gradient/graduated ND filter which only cut off light from part of the image. Example, if you are taking a picture where if you expose the foreground appropriately, the sky will be blown out, because the contrast is too high. One way to solve this is to put a Graduated neutral density filter to reduce the light from the sky, allowing details and saturaion to be better seen in the sky. Using a CP in such a circumstance is inappropriate because the contrast difference will remain the same.

Yes, CP will cut off light, it's just how much. Read my post again before disagreeing.

Thanks for explaining more indepth on the graduated/gradient ND filter, I can't phrase it properly just now, glad you did a better job on it.

[espn]

Originally Posted by student I don't agree. The reason why CP appears not to work is because one do not use it properly.

Urm. I don't agree with this either. I've had my fair share with cheap & expensive CPs, and more than often the cheaper CPs don't show me anything. Although yes, I do agree they do still cut off reflection at certain angles but that's all, I don't see color shits at all. Maybe my technique is wrong. Or I might be wrong.

Originally Posted by student They are all different. ND only reduces light. Stop. Graduated ND reduces light from part of the scene.

Just like the gradient tool in PS, it fills it from one side to another. Useful like taking merlion shots, whereby the base is always over if you expose the merlion correctly, a graduated/gradient ND will help.

[reachme2003]

if i may add, CP does deepens foliage and grass. it works with non-metallic reflections only.

my experience with it is that the shadow areas tend to get darker although metered through the lens and CP filter. i wonder why?

[student]

Originally Posted by espn In short circular polariser should not be cutting off light unlike ND filters, however since it's a filter, there would be some light loss somehow, it's just how much light loss.

I did readyour post carefully.

Indeed you did say that there would be "some light loss somehow", yet you prefaced this statement with "in short CP should not be cutting off light unlike ND filters".

The ambiguity is there, and serves to confuse. In actual fact, CP can act like ND.

[reachme2003]

Originally Posted by student I did readyour post carefully. Indeed you did say that there would be "some light loss somehow", yet you prefaced this statement with "in short CP should not be cutting off light unlike ND filters". The ambiguity is there, and serves to confuse. In actual fact, CP can act like ND.

In practice, CP can function like a non-graduated ND where light reducing is concerned, but it has potential to do more, like deepens blue sky, increase saturation, etc.

[espn]

Originally Posted by student I did readyour post carefully. Indeed you did say that there would be "some light loss somehow", yet you prefaced this statement with "in short CP should not be cutting off light unlike ND filters". The ambiguity is there, and serves to confuse. In actual fact, CP can act like ND.

Ahh yes, my fault. I stand corrected. Thanks for the heads up.

[foxtwo]

Originally Posted by eng_keow .... Read the instructions in the pamphlet which says - look thru the lens and adjust accordingly... which I see no difference when I did that. Took out the cir polarizer and held it to the light and turned the thing round and round but still did not find any difference....

There is a difference. Very slight. Orient yourself 90 degress to the sun. Do it in bright sunny conditions, look at some greenery and the sky (not overcast) and turn the CP SLOWLY. Might take a while but soon you'll see changes in the saturation.
It's easier to spot reduction in glare than saturation changes. You can try that instead. Don't worry, I don't think there are such things as dud CPs.