Circular polarizer or ND filter?


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red_ryder

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I'm going travelling next month, and thinking of buying a filter to complement my new DSLR. I've never used filters before, but from reading magazines I roughly know that a circular polarizer is good for blue skies and cutting out reflections, while an ND is good when the dynamic range is too large for the camera to handle. However, some articles also say that the polarizer can be used as an ND as well? If that is the case, why would anyone buy an ND filter?
 

I'm going travelling next month, and thinking of buying a filter to complement my new DSLR. I've never used filters before, but from reading magazines I roughly know that a circular polarizer is good for blue skies and cutting out reflections, while an ND is good when the dynamic range is too large for the camera to handle. However, some articles also say that the polarizer can be used as an ND as well? If that is the case, why would anyone buy an ND filter?

Depending on how many stops of light you need to cut, you can play around using ND filters... They are very good for adjusting your DOF and to slow down movement like waterfall... etc.

A CPL typically cut about 1 ~ 2 stops of light depending on brand and make. You wouldn't want to cut too much light with the CPL for it's sometimes reduces the light to such an extent that it's difficult to shoot handheld or without subjected to motion blur.
 

CPL and NDs are for 2 different purposes though they look simliar (cut light, well everything cuts light..).

Just like you have swimming trunks and underwear, you can go swimming with trunks.. who would still want buy underwear?
 

the ND you are refering to is a grad ND?

if so then the CP cannot be used to do the same as a grad ND
 

I'm going travelling next month, and thinking of buying a filter to complement my new DSLR. I've never used filters before, but from reading magazines I roughly know that a circular polarizer is good for blue skies and cutting out reflections, while an ND is good when the dynamic range is too large for the camera to handle. However, some articles also say that the polarizer can be used as an ND as well? If that is the case, why would anyone buy an ND filter?

When you talk about using ND when the dynamic range is too large, I guess you are refering to the Grad. ND? A grad. ND is different from a ND filter. For the grad ND, half the filter is darkened and the other half is clear so that you can selectively darken certain areas of the picture such as the sunset sky in order to reduce the dynamic range.

If you are talking about normal ND and polarizer, the fact that a polarizer reduces light input by 1-2 stops makes it work like an ND too, but usually ND filters are cheaper, and they usually come in 1, 2 or 3 stops. Sometimes 1-2 stops is not enough to achieve the effect you want. I've personally used a polarizer like an ND too, when I needed to stop down more than 2 stops of light using my ND4.
 

CPL and NDs are for 2 different purposes though they look simliar (cut light, well everything cuts light..).

Just like you have swimming trunks and underwear, you can go swimming with trunks.. who would still want buy underwear?

Wah... like that also can.... :bsmilie:
 

I'm going travelling next month, and thinking of buying a filter to complement my new DSLR. I've never used filters before, but from reading magazines I roughly know that a circular polarizer is good for blue skies and cutting out reflections, while an ND is good when the dynamic range is too large for the camera to handle. However, some articles also say that the polarizer can be used as an ND as well? If that is the case, why would anyone buy an ND filter?

Simple... ND is neutral. Does not give colour cast. A CP-L may give a colour cast and change the colour of the picture slightly.

Also, ND's have different grades and can cut off lights of (ND2) 1 stop, (ND4)2 stops or (ND8) 3 stops. But the CP-L is standard and only cuts off about 1 - 2 stops.
 

Usually CPLs are used to cut out the reflections from shinny and reflective surfaces like water and glass.
 

They are different filters.

CPL is used for reduce reflection (esp. on water, glass) and also provide 1 stop cut off light. Mainly for beach, pond, items with glass and etc.


ND has grading (2, 4 or 8) and for cut off light only. Mainly for water flowing along stream, water fall, seaside and etc.
 

Without Polarizer,
20060705a.JPG

20060705b.JPG

With Polarizer.

Sorry for the size, will edit into link if you guys finds it disturbing. :embrass:
 

This was taken in the front seat of a cab. Note the reflection from the windscreen is gone, the reflection at the side of the car in front on the right. General sky defination... :)
 

Of course, polarizer spots many brands. Personally for me, a painful switch to B+W, never looked back since. Really is one-part-money-one-part-product. ;)
 

Hi Guys,

If we were to put in the CPL (screw at the front of the lens) does it means that everything I do not need it I will have to take it out and when I need it I will put in again. So in this case how are we going to capture quick shoots? The time of changing in and out will be delayed.

I am very new to CPL and sometime I don't even take it out and shoot all the way, but sometimes the pictures turn out not the way we see it.

If you guys have any ideas to make this works faster, do share with us.
 

Have ample preparations when you are doing your stuffs.

If you are ready to go for sports in the daylight, don't think its too much of a problem.

But if it is on a stormy day or night, then you may want to take it off.

Don't understand when you say what you saw is not what you get. Can eloborate on that?
 

Hi Guys,

If we were to put in the CPL (screw at the front of the lens) does it means that everything I do not need it I will have to take it out and when I need it I will put in again. So in this case how are we going to capture quick shoots? The time of changing in and out will be delayed.

I am very new to CPL and sometime I don't even take it out and shoot all the way, but sometimes the pictures turn out not the way we see it.

If you guys have any ideas to make this works faster, do share with us.

when pictures turn out not the way you see it, this is primarily because the scene's dynamic range is too large for the camera to handle. As you may have realised, your eye has a tremendous sensitivity to a wide dynamic range that is easily 2 times what your camera can record. As such, you may be able to see both shadow details and highlights, but your camera cannot record it.

Under such circumstances, filters such as the Grad ND you have mentioned can come in useful for landscape images, as the sky is often brighter than the foreground. By cutting the amount of light coming from the sky, you compress the dynamic range of the entire image, enabling the camera to capture it as you see it. The other alternative is the add light to the foreground by using flash, or strobes, again compressing the dynamic range. Both methods work by the same principle, to enable the camera to obtain a good exposure for both the foreground and background.

For the CPL, there's no need to remove it at all unless you find yourself short of light. Should you want to shoot reflections, just turn the CPL front-ring until you can see them. Of course, there will be people who will say that putting a CPL will degrade your image, but honestly, it's not even noticeable.

As a last note, I always believe that you should not capture things as your eye sees it, but better than your eye sees it :)
 

Thanks for all the advice.

ANDY may be my eyes are seeing something which STONED has mention, but both of you are great, I will try to learn to use the CPL and take pictures more.
 

I want to buy a ND grad filter for shooting landscapes, but the shops I went to all don't sell. John 3:16 and Alan Photo in Funan both don't have. Where to get Cokin ND grads in Singapore?
 

I want to buy a ND grad filter for shooting landscapes, but the shops I went to all don't sell. John 3:16 and Alan Photo in Funan both don't have. Where to get Cokin ND grads in Singapore?

Cathay is the distributor for Cokin filter systems.
You may have to wait for GND are very hot items.
 

Thanks for all the advice.

ANDY may be my eyes are seeing something which STONED has mention, but both of you are great, I will try to learn to use the CPL and take pictures more.

Yes.

I think a picture speaks a thousand words. Therefore used a visual representation. :)
 

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