Adjustable ND filter question

PatrickJamesYu

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Hi I'm looking for a ND filter that stops a very very heavy amount of stops.
I'm considering a ND2-ND400 variable filter.
Will a rotating filter like this, be it's true ND stop number, all the way through the lens? (top to bottom?)

Looking up reviews, everybody seems to be using these variable filters on 50mm, 85mm, 105mm and so on.
I plan to use it on my 17-70 f2.8
Primarily in the 17mm range.
This is quite wide so I'm wondering if the ND grade will be even from top to bottom with a rotating variable design like this.
 

tirediron

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If I understand your post correctly, I think you're talking about two different things. A variable ND filter, such as this Singh-Ray is NOT a graduated filter, that is: The density or amount of light blocked does not vary from top to bottom, but rather is constant across the viewing surface, increasing or decreasing in density as you rotate the front filter element with respect to the rear.

A graduated neutral-density (G-ND) is a filter which has a dark, neutral-density layer at one end which gradually reduces in intensity as it moves across the filter surface. These can be either regular, round, screw-on filters, or, more commonly, the gel/acetate style such as this Cokin example.
 

analog.universe

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I researched variable ND filters for a while and ultimately decided not to buy one. They accomplish their effect by rotating two polarizing filters with respect to each other. It's effective as an ND, and the density is even across the frame, but you now have to deal with double polarizing the scene also. In examples I saw this could sometimes lead to unpredictable effects like color shifts in skies from one side of the frame to the other... The effects were more varied on wide angles (just like with regular polarizers).

If you want very heavy ND at 17mm, I'd suggest the B+W 110, 10-stop filter. I use one and it does wonderfully. Great construction, great glass, no frills.. and lets me leave the shutter open for several minutes in bright sun.
 

TheBiles

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I think he was worried about how CPLs have a tenancy to produce mixed results at ultra-wide angles. This shouldn't be a problem with a vari-ND, though.

Sent from my Galaxy Nexus using Tapatalk
 

analog.universe

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I think he was worried about how CPLs have a tenancy to produce mixed results at ultra-wide angles. This shouldn't be a problem with a vari-ND, though.

Sent from my Galaxy Nexus using Tapatalk

This is one of the main problems with vari-ND's that I was talking about, which ultimately prevented me from owning one.
 

TheBiles

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Even though the scene is double-polarized, the light loss is still constant throughout, right? For example, you wouldn't have half of your sky blown out with the other half properly exposed? Even if the colors are off, is exposure impacted that much?

Sent from my Galaxy Nexus using Tapatalk
 

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