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Technical Questions

ND and CP

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mdecaprio
 
Posts: 32

ND and CP

Post Sun May 11, 2008 7:24 pm


I am wondering what (if any) advantages ND has over CP. I can understand if you were using a CP and it could not slow the shutter speed down enough one might need to use an ND4 or ND6 or more.

But for general use, is there any advantage of using something like an ND2 over a CP? Perhaps the more appropriate question is, in what situations would an ND2 be more appropriate than a CP or vice versa?
Mike
Canon 40D
Canon EOS 350D
EF 70-200/f4 L
EF-S 17-55 f2.8
EF 100/f2.8 macro
EF 50/f1.8
EF-S 18-55

prinothcat
 
Posts: 662

Re: ND and CP

Post Sun May 11, 2008 8:29 pm


First of all, ND = Neutral Density? CP = Circular polarizer?
If so your talking apples and oranges. In brief, a polarizer cuts the glare and reflection from cross polarized light. ND's come in multiple flavors. A full ND is used to drop the overall exposure value in order to either shoot at a lower ISO, or lower shutter speeds in very bright lighting. Htis can also be achieved with exposure compensation in camera. The classic example of this is blurred water in full light. ND's also come in graduated form where 1/2 is darkened and 1/2 is clear. Grads come in different grades of shading, as well as hard transitions and soft transitions. These are used to even light conditions when parts of the frame are much brighter than the rest. The main use of ND grads these days is to compensate for the limited exposure latitude of digital sensors. Film was much better at handling images that had an extreme range of light to dark (exposure latitutde). Should you be considering ND grads look into square ones that can be moved in front of the lens to place the transition point to it's maximum advantage. Screw in ND grads force one to recompose the image based on a fixed transition point. So yes, there are definite advantages to ND's over a CP.

jellophoto
 
Posts: 192

Re: ND and CP

Post Wed May 14, 2008 8:41 pm


I tend to use NDs most of the time. Brings out the drama in cloudy skys and also drops the light levels enough for my lense to be able to freeze water to get the swirly misty effect. Cheap square Cokins work for me, easily scratched , but easily replaced.

Regards John


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