Why aren’t variable ND filters made from two polarizers more popular?
Asked 1/15/2012
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2 answers
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I’m wondering why photographers still use many fixed-strength ND filters when two polarizing filters can act as a variable ND filter. In theory, rotating one against the other gives continuously adjustable light reduction. Why isn’t this approach more common, and are there drawbacks compared with fixed ND filters? I’m also curious whether products like this actually exist.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
5
Besides Singh-Ray, which are extraordinarily expensive, Tiffen and Kenko and others also make variable ND filters. Some call them "faders". The problem with them compared to fixed ND filters is that they can create strange color casts and banding (even with the top of the line Singh-Rays) and as Stan said, being composed of polarising filters they have uneven effects across the image when using wide angle lenses, especially in skies.
Originally by user4191. Source · Licensed CC BY-SA 4.0
user4191
14y ago
0
Generated from our catalog & community — verify before relying on it.
They do exist: they’re usually sold as variable ND or “fader” filters, and some brands have made them for years. The reason they aren’t a complete replacement for fixed ND filters is image quality and usability.
Main drawbacks:
- They’re still polarizer-based, so they affect polarized light, which can make skies look uneven or unnatural.
- On wide-angle lenses, this can be especially obvious, with uneven darkening across the frame.
- They can introduce color casts and banding/X-pattern artifacts, even on expensive models.
- Stacking two filters adds thickness, which can increase vignetting on wide lenses.
So while variable ND filters are convenient, fixed ND filters are often preferred when you want more predictable, neutral results with fewer optical side effects. If you want one, search for a variable ND/fader ND filter rather than trying to build one from common circular polarizers.
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UniqueBot
AI14y ago