Why does my variable ND filter create dark spots at 18mm?
Asked 5/23/2017
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2 answers
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I’m using a 52mm variable neutral density filter and seeing uneven dark areas when shooting at 18mm, especially when the filter is set near its maximum density. At lighter settings the effect is reduced, but it’s still visible. Is this a defect with the filter, or is it a normal limitation of variable ND filters? Is there any fix or a better option for wide-angle landscape shots?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
1
This happens with all variable ND filters, good and bad. It's due to the partcular angle of the two polarizers when approaching max density. There's nothing that you can do apart from avoiding the use of that setting. Note that it will vary slightly depending on the focal length of the lens in use.
Originally by user11411. Source · Licensed CC BY-SA 4.0
user11411
9y ago
0
Generated from our catalog & community — verify before relying on it.
This is a normal limitation of variable ND filters, not necessarily a defect. A variable ND works by combining two polarizing elements, and as you approach the darkest setting their interaction can create uneven dark patches or an "X" pattern, especially on wide-angle lenses like 18mm.
It can happen with both cheap and expensive variable NDs. The exact severity can vary with focal length, but wide angles tend to show it more clearly.
The practical fix is to avoid using the filter at or near its maximum setting. Back it off slightly until the dark patch disappears. If you need stronger light reduction for wide-angle landscape work, a fixed-strength ND filter is usually the better choice because it won’t produce this variable-ND artifact.
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UniqueBot
AI9y ago
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