Luminous Landscape Forum
Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Greg D on July 07, 2009, 11:55:10 am
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I've seen it suggested before that a linear ploarizer on top of a circular one makes a good variable neutral density filter. What are the drawbacks to using this method? I would assume there would still be the issue of darkening in the top center of the frame that one normally sees with a polarizer, correct? Other problems? Sounds too easy.......
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I've seen it suggested before that a linear ploarizer on top of a circular one makes a good variable neutral density filter. What are the drawbacks to using this method? I would assume there would still be the issue of darkening in the top center of the frame that one normally sees with a polarizer, correct? Other problems? Sounds too easy.......
You'll probably have vignetting as the two stacked filters will be thick enough to be problematic on wide angle lenses. While I haven't seen the Singh-Ray Vari ND filter ( http://www.singh-ray.com/varind.html (http://www.singh-ray.com/varind.html) ), I believe that it's essentially two polarizers (circular & linear) stacked together. I might be wrong?
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I've done a fair bit of it, using a step-up ring from a smaller filter on the lens to a larger on the ring to overcome vignetting when I'm shooting a WA lens.
The biggest problem I've encountered is color shift. You'll get a decided green cast...... okay, make that a sickly olive cast..... if you mix brands of filters, and especially if they're cheaper filters. Best I've tried for beating the color cast is B+W.
It's not a perfect system, but good enough to try when conditions warrant- if you already own the filters and happen to have them in your camera bag. If buying new filters for the job, I'd forgo the extra polarizers and move directly to a variable ND.
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I've done a fair bit of it, using a step-up ring from a smaller filter on the lens to a larger on the ring to overcome vignetting when I'm shooting a WA lens.
The biggest problem I've encountered is color shift. You'll get a decided green cast...... okay, make that a sickly olive cast..... if you mix brands of filters, and especially if they're cheaper filters. Best I've tried for beating the color cast is B+W.
It's not a perfect system, but good enough to try when conditions warrant- if you already own the filters and happen to have them in your camera bag. If buying new filters for the job, I'd forgo the extra polarizers and move directly to a variable ND.
FWIW, David Mantripp (drm: profile (http://luminous-landscape.com/forum/index.php?showuser=12697))), reports that the Singh-Ray Vari ND also suffers from color shift.
Here's the link to his blog: http://www.snowhenge.net/index.php/pblog/2008/03/ (http://www.snowhenge.net/index.php/pblog/2008/03/)
However, I cannot recommend the Singh-Ray filter, as it introduces some very nasty colour shifts and irregular darkening. This is partly due to the design, based on two polarisers, but frankly, it is way over-priced and clumsy to use. It seems worse on the E-3 than the E-1 or E-400, but it isn't brilliant on them either.
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If it's based on two polarizers, fuggedaboudit. Been there done that. I'd simply go back to packing ND filters before I'd spend extra for it. Using two B+W's does help eliminate the color cast, but at the same time colors get a little "muddy" for lack of a better term. You'll end up bumping contrast, or better yet using the black controls on each color in Photoshop's Selective Color adjustment.
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I've seen it suggested before that a linear ploarizer on top of a circular one makes a good variable neutral density filter. What are the drawbacks to using this method? I would assume there would still be the issue of darkening in the top center of the frame that one normally sees with a polarizer, correct? Other problems? Sounds too easy.......
Wouldn't 2 polarizers of any type do the job? It would be one heck of an ND filter, you'd lose 3-4 stops before even changing them relative to each other.
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In my experience you'll do fine with two linears, but two circs doesn't work nearly as well as other combos. You do get the 3-4 stop light loss as a minimum with two circs, but I don't like the results. As an aside or an elaboration, I've had better results in that range using a 2-stop ND filter along with a circ.